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研究者総覧 研究者詳細 ホーム 日本語 English 研究者総覧 メニュー English Page 名古屋大学HPへ ホームへ 基本情報 ▼ ◆ 基本情報 ◆ 学位 ◆ 研究キーワード ◆ 研究分野 ◆ 現在の研究課題とSDGs ◆ 経歴 ◆ 学歴 ◆ 所属学協会 ◆ 委員歴 ◆ 受賞 研究活動 ▼ ◆ 論文 ◆ 書籍等出版物 ◆ MISC ◆ 講演・口頭発表等 ◆ 共同研究・競争的資金等の研究課題 ◆ 科研費 ◆ 産業財産権 教育活動 ▼ ◆ 担当経験のある科目(本学) ◆ 担当経験のある科目(本学以外) 社会貢献 ▼ ◆ 社会貢献活動 ◆ メディア報道 × 2024/04/24 更新 基本情報 ◆ 基本情報 ◆ 学位 ◆ 研究キーワード ◆ 研究分野 ◆ 現在の研究課題とSDGs ◆ 経歴 ◆ 学歴 ◆ 所属学協会 ◆ 委員歴 ◆ 受賞 研究活動 ◆ 論文 ◆ 書籍等出版物 ◆ MISC ◆ 講演・口頭発表等 ◆ 共同研究・競争的資金等の研究課題 ◆ 科研費 ◆ 産業財産権 教育活動 ◆ 担当経験のある科目 (本学) ◆ 担当経験のある科目 (本学以外) 社会貢献 ◆ 社会貢献活動 ◆ メディア報道 2024/04/24 更新 アマノ ヒロシ 天野 浩 AMANO, Hiroshi 所属 未来材料・システム研究所 附属未来エレクトロニクス集積研究センター 未来デバイス部 教授 大学院担当 大学院工学研究科 学部担当 工学部 職名 教授 連絡先 ホームページ http://www.semicond.nuee.nagoya-u.ac.jp/index.html 外部リンク 学位 学位 7 名誉博士号 ( 2017年1月 グアテマラパジェ大学 ) 名誉博士号 ( 2016年6月 モンゴル国立大学 ) 名誉博士号 ( 2016年5月 フランスオーベルニュ大学ブレイズパスカル大学 ) 名誉博士号 ( 2016年4月 イタリアパドバ大学 ) 名誉博士号 ( 2015年9月 スウェーデンリンショーピング大学 ) 名誉博士号 ( 2015年6月 ロシアノボシビルスク州立大学 ) 工学博士 ( 1989年1月 名古屋大学 ) ▼全件表示 学位の先頭へ▲ 研究キーワード 研究キーワード 10 発光ダイオード, レーザダイオード, トランジスタ, 太陽電池, 化合物半導体結晶成長, 半導体デバイス物理, ナノ構造 発光ダイオード 太陽電池 半導体デバイス物理 化合物半導体結晶成長 レーザダイオード ナノ構造 トランジスタ パワーデバイス ミリ波 マイクロ波デバイス 研究キーワードの先頭へ▲ 研究分野 研究分野 1 その他 / その他 / 電子・電気材料工学 研究分野の先頭へ▲ 現在の研究課題とSDGs 現在の研究課題とSDGs 3 安心・安全で省エネルギー化に貢献する半導体デバイス Ⅲ族窒化物半導体の結晶成長とデバイス応用 卓越大学院DIIプログラム 現在の研究課題とSDGsの先頭へ▲ 経歴 経歴 15 名古屋大学未来材料・システム研究所 未来エレクトロニクス集積研究センター 未来エレクトロニクス集積研究センターセンター長 2015年10月 - 現在 詳細を見る 国名:日本国 名古屋大学 未来材料・システム研究所 附属未来エレクトロニクス集積研究センター 未来デバイス部 教授 2015年10月 - 現在 詳細を見る researchmap 名城大学特別栄誉教授 2015年7月 - 現在 詳細を見る 国名:日本国 名城大学 2015年7月 - 現在 詳細を見る researchmap 名古屋市立大学 客員教授 2015年4月 - 2016年3月 詳細を見る 国名:日本国 名古屋大学特別教授 2015年3月 - 現在 詳細を見る 国名:日本国 名古屋大学 教授 2015年3月 - 現在 詳細を見る researchmap 中国清華大学 名誉教授 2014年11月 - 現在 詳細を見る researchmap 名古屋大学 大学院工学研究科 共通/大学院工学研究科) 赤﨑記念研究センター センター長 2011年4月 - 現在 名古屋大学 大学院工学研究科 共通/大学院工学研究科) 赤﨑記念研究センター センター長 2011年4月 - 現在 詳細を見る researchmap 名古屋大学 工学研究科電子情報システム専攻 教授 2010年4月 - 2015年10月 詳細を見る 国名:日本国 名城大学理工学部教授 2002年4月 - 2010年3月 詳細を見る 国名:日本国 名城大学理工学部助教授 1998年4月 - 2002年3月 詳細を見る 国名:日本国 名城大学理工学部講師 1992年4月 - 1998年3月 詳細を見る 国名:日本国 名古屋大学助手(工学部) 1988年4月 - 1992年3月 詳細を見る 国名:日本国 ▼全件表示 経歴の先頭へ▲ 学歴 学歴 3 名古屋大学 工学研究科 電気工学・電気工学第二及び電子工学専攻 1985年4月 - 1988年3月 詳細を見る 国名: 日本国 名古屋大学 工学研究科 電気工学・電気工学第二及び電子工学専攻 1983年4月 - 1985年3月 詳細を見る 国名: 日本国 名古屋大学 工学部 電子工学科 1979年4月 - 1983年3月 詳細を見る 国名: 日本国 学歴の先頭へ▲ 所属学協会 所属学協会 34 日本学士院 会員 2022年12月 - 現在 IEEE メンバー 2022年1月 - 現在 中国工程院 外国籍院士 2019年11月 - 現在 National Academy of Inventors,USA NAI Fellow 2017年10月 - 現在 照明学会 名誉会員 2016年9月 - 現在 American Physical Society フェロー 2015年9月 - 現在 日本工学アカデミー 会員 2015年6月 - 現在 日本化学会 名誉会員 2015年6月 - 現在 NAE(United States National Academy of Engineering) 2015年6月 - 現在 電気学会 名誉員 2015年5月 - 現在 日本表面科学会 特別栄誉会員 2015年5月 - 現在 日本物理学会 名誉会員 2015年4月 - 現在 電子情報通信学会 名誉員 2015年3月 - 現在 電子情報通信学会 名誉員 2014年12月 - 現在 Institute of Physics UK Fellow 2014年12月 - 現在 Material Research Society Regular Member 2010年1月 - 現在 応用物理学会 名誉会員 1984年10月 - 現在 Optical Society of America SPIE 応用物理学会 Fellow、名誉会員 Institute of Physics Fellow American Physical Society 詳細を見る researchmap 電気学会 詳細を見る researchmap 電子情報通信学会 詳細を見る researchmap 照明学会 詳細を見る researchmap 日本表面科学会 詳細を見る researchmap 日本物理学会 詳細を見る researchmap 日本工学アカデミー 詳細を見る researchmap 日本化学会 詳細を見る researchmap 応用物理学会 詳細を見る researchmap SPIE 詳細を見る researchmap Optical Society of America 詳細を見る researchmap NAE(United States National Academy of Engineering) 詳細を見る researchmap Material Research Society 詳細を見る researchmap ▼全件表示 所属学協会の先頭へ▲ 委員歴 委員歴 30 IWUMD-2017 組織委員長 2016年10月 - 2017年12月 国立研究会開発法人産業術総合研究所 柱冠フェロー 2016年8月 - 現在 詳細を見る 団体区分:政府 International Solid State Lighting Alliance 国際諮問委員 2016年8月 - 現在 詳細を見る 団体区分:学協会 OPIC2017 組織委員 2016年8月 - 現在 詳細を見る 団体区分:学協会 国際物理オリンピック日本大会 組織委員会副委員長 2016年5月 - 2023年8月 詳細を見る 団体区分:その他 日本結晶成長学会 評議員 2016年4月 - 2019年3月 詳細を見る 団体区分:学協会 33rd International Conference on the Physics of Semiconductors国際諮問委員会 委員長 2015年9月 - 2016年8月 ・結晶成長の科学と技術第161委員会 委員 2015年8月 - 2016年3月 2015 Rusnanoprize Award Committee Member 2015年7月 - 現在 2015 Rusnanoprize Award Committee Member 2015年7月 - 現在 詳細を見る researchmap 2015 Rusnanoprize Award Committee Member 2015年7月 - 現在 詳細を見る researchmap Optics & Photonics International Congress 2016組織委員会 委員 2015年7月 - 2016年6月 江崎玲於奈賞委員会 委員 2015年6月 - 現在 詳細を見る 団体区分:その他 日本フォトニクス協議会 JPC関西 特別顧問 2015年5月 - 現在 詳細を見る 団体区分:その他 大阪大学光科学センター 特別顧問 2015年5月 - 2017年9月 ISPlasma2016/IC-PLANT2016組織委員会 委員長 2015年5月 - 2016年4月 組織委員会委員 2014年7月 - 2015年3月 ISCS2014 Regional program chair 2013年4月 - 現在 Program Committee Chair 2013年4月 - 2014年3月 OPIC2013 組織委員 2012年7月 - 現在 OPIC2013 組織委員 2012年7月 - 現在 詳細を見る researchmap レーザ学会 専門委員会 2012年5月 - 2015年3月 産業用LED応用研究会 委員長 2012年4月 - 現在 プログラム委員会副委員長 2012年2月 - 2012年4月 4th International Symposium on Growth of III-Nitrides Program Committee Chair 2011年7月 - 2012年7月 ICMOVPE-XVI International Advisory COmmittee 2011年6月 - 2012年5月 実行委員長 2011年4月 - 2012年10月 名古屋市科学館企画調査委員会 企画調査委員 2010年8月 - 現在 電子部品・材料研究専門委員会 専門委員 2010年5月 - 2012年5月 ワイドギャップ半導体光・電子デバイス第162委員会 特別顧問 2010年4月 - 2017年3月 ▼全件表示 委員歴の先頭へ▲ 受賞 受賞 36 卓越教授 2023年4月 名古屋大学 卓越教授 詳細を見る 受賞国:日本国 特別教授 2019年10月 広島大学 特別教授 詳細を見る 受賞国:日本国 応用物理学会化合物半導体エレクトロニクス業績賞(赤﨑勇賞) 2016年3月 応用物理学会 青色及び紫外光デバイスの開発 天野 浩 詳細を見る 受賞区分:国内学会・会議・シンポジウム等の賞 受賞国:日本国 丸八会顕彰 2015年10月 丸八会 詳細を見る 受賞国:日本国 第10回業績賞及び赤﨑勇賞 2015年10月 日本結晶成長学会 高品質窒化物半導体の創出と青色・紫外光素子の実現 天野 浩 詳細を見る 受賞区分:国内学会・会議・シンポジウム等の賞 受賞国:日本国 2015 Asia Game Changers 2015年10月 Asia Society 詳細を見る 受賞区分:国内外の国際的学術賞 受賞国:アメリカ合衆国 愛知県名誉県民 2015年9月 愛知県 詳細を見る 受賞国:日本国 産学官連携功労者表彰 日本学術会議会長賞, 2015年8月 日本学術会議会長 「短波長紫外LED」の開発 天野 浩 詳細を見る 受賞国:日本国 浜松市名誉市民 2015年7月 浜松市 詳細を見る 受賞国:日本国 中日文化賞 2015年5月 中日新聞 詳細を見る 受賞国:日本国 科学技術分野の文部科学大臣表彰 科学技術賞研究部門 2015年4月 文部科学大臣 詳細を見る 受賞国:日本国 特別教授 2015年4月 名古屋大学 特別教授 詳細を見る 受賞国:日本国 特別栄誉教授 2015年4月 名城大学 特別栄誉教授 詳細を見る 受賞国:日本国 日本スウェーデン協会 名誉会員 2015年3月 日本スウェーデン協会 詳細を見る 受賞国:日本国 電子情報通信学会 特別功績賞 2015年3月 電子情報通信学会 詳細を見る 受賞国:日本国 名古屋市学術表彰 2015年1月 名古屋市 詳細を見る 受賞国:日本国 愛知県学術顕彰 2015年1月 愛知県 詳細を見る 受賞国:日本国 静岡県民栄誉賞 2015年1月 静岡県 詳細を見る 受賞国:日本国 ノーベル物理学賞 2014年12月 ノーベル財団 詳細を見る 受賞国:スウェーデン王国 文化功労者顕彰 2014年11月 文部科学大臣 詳細を見る 受賞国:日本国 文化勲章 2014年11月 首相 詳細を見る 受賞国:日本国 APEX/JJAP編集貢献賞 2014年3月 応用物理学会 詳細を見る 受賞国:日本国 IOP Fellow 2011年10月 Institute of Physics 詳細を見る 受賞国:グレートブリテン・北アイルランド連合王国(英国) 英国物理学会 フェロー 2011年10月 天野 浩 詳細を見る 受賞国:グレートブリテン・北アイルランド連合王国(英国) ナイスステップな研究者2009 2009年12月 文部科学省 科学技術政策研究所 詳細を見る 受賞国:日本国 ナイスステップな研究者2009 2009年12月 科学技術・政策研究所 青色及び紫外光デバイスの開発 天野 浩 詳細を見る 受賞国:日本国 応用物理学会フェロー 2009年9月 応用物理学会 詳細を見る 受賞国:日本国 日本結晶成長学会論文賞 2008年11月 日本結晶成長学会 詳細を見る 受賞国:日本国 第1回 P&I パテント・オブ・ザ・イヤー 2004年11月 東京工業大学精密工学研究所 詳細を見る 受賞国:日本国 SSDM論文賞 2003年9月 SSDM 詳細を見る 受賞国:日本国 武田賞 2002年11月 竹田財団 詳細を見る 受賞国:日本国 丸文学術賞 2001年3月 丸文財団 詳細を見る 受賞国:日本国 英国Rank賞 1998年12月 Rank Foundation 応用物理学会賞C(会誌賞) 1998年9月 応用物理学会 詳細を見る 受賞国:日本国 米国IEEE/LEOS エンジニアリングアチーブメント賞 1996年11月 オプトエレクトロニクス会議特別賞 1994年7月 ▼全件表示 受賞の先頭へ▲ 論文 論文 827 Metastable atomic-ordered configurations for Al1/2Ga1/2N predicted by Monte-Carlo method based on first-principles calculations Gueriba, JS; Mizuseki, H; Cadatal-Raduban, M; Sarukura, N; Kawazoe, Y; Nagasawa, Y; Hirano, A; Amano, H JOURNAL OF PHYSICS-CONDENSED MATTER 36 巻 ( 13 ) 2024年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Journal of Physics Condensed Matter Metastability of Aln/12Ga1−n/12N (n = 2–10: integer) with the 1–2 monolayer (ML) in-plane configuration towards the c [0001] direction has been demonstrated recently. To theoretically explain the existence of these metastable structures, relatively large calculation cells are needed. However, previous calculations were limited to the use of small calculation cell sizes to estimate the local potential depth (∆σ) of ordered Al1/2Ga1/2N models. In this work, we were able to evaluate large calculation cells based on the interaction energies between proximate Al atoms (δEAl–Al) in AlGaN alloys. To do this, δEAl–Al values were estimated by first-principles calculations (FPCs) using a (5a1 × 5a2 × 5c) cell. Next, a survey of the possible ordered configurations using various large calculation cell models was performed using the estimated δEAl–Al values and the Monte-Carlo method. Then, various ∆σ values were estimated by FPCs and compared with the configurations previously reported by other research groups. We found that the ordered configuration obtained from the (4a1 × 2a2 × 1c) calculation cell (C42) has the lowest ∆σ of −9.3 meV/cation and exhibited an in-plane configuration at the c(0001) plane having (–Al–Al–Ga–Ga–) and (–Al–Ga–) sequence arrangements observed along the m{11̄00} planes. Hence, we found consistencies between the morphology obtained from experiment and the shape of the primitive cell based on our numerical calculations. DOI: 10.1088/1361-648X/ad1137 Web of Science Scopus PubMed Study on Degradation of Deep-Ultraviolet Laser Diode Zhang, ZY; Yoshikawa, A; Kushimoto, M; Sasaoka, C; Amano, H PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE 2024年2月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Physica Status Solidi (A) Applications and Materials Science The degradation of an AlGaN-based deep-ultraviolet laser diode during operation is studied. A rapid increase in threshold current without any facet mirror damage under direct current stress below the threshold current is observed, which is considered to limit the lifetime of continuous wave lasing to the level of seconds. The evolution of current–light and current–voltage characteristics suggests that the dominant mechanism of degradation is the increased loss of carriers before they can reach the active layer, i.e., the decrease in carrier injection efficiency. The decrease in emission intensity, which is more pronounced at lower current densities, and subsequent increase in sub-threshold current indicate the increase in defect density under current stress, which is similar to the well-analyzed degradation mechanism found in AlGaN-based light-emitting diodes. DOI: 10.1002/pssa.202300946 Web of Science Scopus Sn-doped n-type GaN layer with high electron density of 1020 cm-3 grown by halide vapor phase epitaxy Hamasaki, K; Ohnishi, K; Nitta, S; Fujimoto, N; Watanabe, H; Honda, Y; Amano, H JOURNAL OF CRYSTAL GROWTH 628 巻 2024年2月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Journal of Crystal Growth A Sn-doped n-type GaN layer with a high electron density of 2 × 1020 cm−3 and a low resistivity of 8.7 × 10−4 Ω∙cm was grown by halide vapor phase epitaxy (HVPE). Sn doping was performed through the reaction between Sn metal and HCl gas. The Sn concentration markedly increased with decreasing growth temperature and the activation energy of Sn desorption from the GaN surface was found to be 4.1 eV. Smooth surfaces were obtained by introducing the Sn precursor even though the samples were grown at a low temperature of 905 °C, suggesting that Sn atoms act as surfactants and promote the migration of Ga adatoms. Almost all the Sn atoms act as donors in GaN below the Sn concentration of 2 × 1020 cm−3. These results indicate that using the Sn donor is promising for fabricating low-resistivity n-type GaN substrates by HVPE. DOI: 10.1016/j.jcrysgro.2023.127529 Web of Science Scopus Impacts of off-angle and off-direction on surface morphology of GaN grown by metalorganic vapor phase epitaxy on (0001) GaN substrate Watanabe, H; Nitta, S; Ando, Y; Ohnishi, K; Honda, Y; Amano, H JOURNAL OF CRYSTAL GROWTH 628 巻 2024年2月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Journal of Crystal Growth DOI: 10.1016/j.jcrysgro.2023.127552 Web of Science Scopus Impact of unintentionally formed compositionally graded layer on carrier injection efficiency in AlGaN-based deep-ultraviolet laser diodes Zhang Z., Yoshikawa A., Kushimoto M., Aoto K., Sasaoka C., Amano H. Applied Physics Letters 124 巻 ( 6 ) 2024年2月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Applied Physics Letters Increasing the injection efficiency, a critical factor constraining the reduction in threshold current in AlGaN-based deep-ultraviolet laser diodes, represents one of the paramount remaining technical challenges. In this study, the impact of compositionally graded layers that were unintentionally formed at the interface between the p-cladding and the core layer on carrier injection efficiency was analyzed. Experimental evaluations using laser diodes have shown that the elimination of an unintentionally formed layer increases the injection efficiency above the threshold current, from the conventional 3% to 13%. It has been postulated that the electron overflow toward the p-side exerts a substantial deleterious effect on the injection efficiency. An improvement in this aspect is achieved by increasing the electron-blocking capability due to the improved interface abruptness between the p-cladding layer and the core layer. The lasing threshold was strongly reduced, and characteristic temperature increased from 76 to 107 K for the improved devices. DOI: 10.1063/5.0184543 Scopus Optical activation of praseodymium ions implanted in gallium nitride after ultra-high pressure annealing Ito, S; Sato, S; Bockowski, M; Deki, M; Watanabe, H; Nitta, S; Honda, Y; Amano, H; Yoshida, K; Minagawa, H; Hagura, N NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS 547 巻 2024年2月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms Lanthanide (Ln)-implanted gallium nitride (GaN) semiconductors have a variety of potential applications as light-emitting devices and quantum light sources, but their optical properties are not well understood. In this study, we investigate the room temperature optical properties of praseodymium (Pr) ion implanted single-crystal GaN and their changes upon ultrahigh pressure annealing (UHPA) up to 1480 °C. Photoluminescence (PL) spectra, luminescence transition lifetime, and excitation cross section of the implanted Pr ions are analyzed. In addition, the recovery of implantation-induced damage and the thermal diffusion of implanted Pr ions by UHPA are investigated by X-ray diffraction, Raman spectroscopy, and secondary ion mass spectrometry. The results show that the implantation damage is recovered by annealing at temperatures above 1200 °C, but Pr ions thermally diffuse to the surface as the annealing temperature increases. The annealing temperature at which a maximum PL intensity is obtained increases with increasing the implantation dose. However, the PL intensity decreases in all cases after annealing at 1480 °C, indicating that a quenching factor is dominant in this temperature range. DOI: 10.1016/j.nimb.2023.165181 Web of Science Scopus Impurity reduction in lightly doped n-type gallium nitride layer grown via halogen-free vapor-phase epitaxy Kimura, T; Shimazu, H; Kataoka, K; Itoh, K; Narita, T; Uedono, A; Tokuda, Y; Tanaka, D; Nitta, S; Amano, H; Nakamura, D APPLIED PHYSICS LETTERS 124 巻 ( 5 ) 2024年1月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Applied Physics Letters The development of gallium nitride (GaN) vertical-type metal-oxide-semiconductor field-effect transistors and p-i-n diode devices has gathered increasing attention. These devices require an n-type drift layer with a low doping level of 1016 cm−3 or less, minimized point defects inhibiting electron conduction, and a layer approximately 10 μm thick. Therefore, a practical method with a growth rate of at least several tens of μm/h and impurity concentrations of less than 1015 cm−3, except for that of dopants, is necessary. Halogen-free vapor-phase epitaxy (HF-VPE) has a high growth rate suitable for fabricating thick drift layers and utilizes a simple reaction between Ga vapor and ammonia gas (without a corrosive halogen gas), resulting in lower impurity levels. Herein, we eliminated the quartz content from the high-temperature zone to reduce the excess unintentional Si doping and identified that the nitrile gloves used for the growth preparation are other impurity contamination sources. We obtained a lightly n-type ([Si]=∼1016 cm−3) GaN layer, in which C, O, B, Fe, Mg, Al, Ca, Cr, Zn, Ni, Mn, and Ti impurity contents were below the detection limits of secondary ion mass spectrometry. Deep-level transient spectroscopy revealed that electron traps at EC − 0.26 and at EC − 0.59 eV were 2.7 × 1013 and 5.2 × 1014 cm−3, respectively. Moreover, the Hall effect analysis showed the acceptor-type defect-compensating donor content as approximately 2.7 × 1015 cm−3, resulting in a high electron mobility of HF-VPE GaN in the 30-710 K temperature range. Furthermore, we identified the Ca impurity as a deep acceptor, another killer defect leading to mobility collapse. DOI: 10.1063/5.0191774 Web of Science Scopus Droop and light extraction of InGaN-based red micro-light-emitting diodes Park, JH; Pristovsek, M; Cai, WT; Kumabe, T; Choi, SY; Lee, DS; Seong, TY; Amano, H SEMICONDUCTOR SCIENCE AND TECHNOLOGY 39 巻 ( 1 ) 2024年1月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Semiconductor Science and Technology In this letter, we investigate the impact of periphery, width, length and area on the external quantum efficiency (EQE) of stripe-type InGaN-based red micro-light-emitting diodes (µLEDs). A longer periphery resulted in a higher light extraction efficiency ( η e ) via the sidewall regardless of the area of the µLEDs. However, as the injection current increased a somewhat larger efficiency droop was observed at the longer periphery due to current crowding. Additionally, larger µLEDs experienced more self-heating than smaller ones, resulting in a red shift of wavelengths and a larger efficiency droop. When the current density exceeded 100 A cm−2, the EQE ratio of smaller-area μLEDs to larger-area ones increased significantly due to the difference in efficiency droop. Besides, a short light propagation length and a long emission width yielded a higher η e . Hence, the periphery, width, length and area of the µLEDs determine EQE, which provides insight into the pixel design of µLED displays. DOI: 10.1088/1361-6641/ad0b88 Web of Science Scopus Temperature Dependence of α-Particle Detection Performance of GaN PIN Diode Detector Nakagawa, H; Hayashi, K; Miyazawa, A; Honda, Y; Amano, H; Aoki, T; Nakano, T SENSORS AND MATERIALS 36 巻 ( 1 ) 頁: 169 - 176 2024年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Sensors and Materials Group-III nitride semiconductors, such as gallium nitride (GaN), have been proposed as novel materials for radiation detection owing to their wide bandgap and their ability to operate at high temperatures. In this study, the radiation detection properties of GaN PIN diode detectors were evaluated at high temperatures (~573 K). The energy spectrum peak profiles of241Am α-particles were obtained at different temperatures, confirming the operation of GaN PIN diodes up to 573 K. The peak positions shifted toward the lower-energy side and the full width at half maximum (FWHM) of the detection energy peak improved with increasing temperature. Furthermore, the variation in electron carrier mobility–lifetime product (μeτe) between 293 and 573 K was not significant. These results indicate the potential high-temperature operation of group-III nitride semiconductors. Additionally, the variation in each detection characteristic was caused by increasing the atmospheric temperature, which affected the mobility, lattice scattering, bandgap, and built-in potential differently. DOI: 10.18494/SAM4647 Web of Science Scopus Demonstration of AlGaN-on-AlN p-n Diodes With Dopant-Free Distributed Polarization Doping Kumabe T., Yoshikawa A., Kawasaki S., Kushimoto M., Honda Y., Arai M., Suda J., Amano H. IEEE Transactions on Electron Devices 2024年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:IEEE Transactions on Electron Devices Nearly ideal vertical Al
The effect of dry etching condition on the performance of blue micro light-emitting diodes with reduced quantum confined Stark effect epitaxial layer
Park Jeong-Hwan, Cai Wentao, Cheong Heajeong, Ushida Yasuhisa, Lee Da-Hoon, Ando Yuto, Furusawa Yuta, Honda Yoshio, Lee Dong-Seon, Seong Tae-Yeon, Amano Hiroshi JOURNAL OF APPLIED PHYSICS 131 巻 ( 15 ) 2022年4月 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Journal of Applied Physics As the size of micro light-emitting diodes (μLEDs) decreases, μLEDs encounter etching damage especially at the sidewalls that critically affects their properties. In this study, we investigated the influence of etching bias power (Pbias) on the performance of μLEDs and found that the current-voltage and light output-current characteristics of μLEDs were enhanced when Pbias was reduced. It was shown that at low Pbias, the chemical reaction between etching gas and gallium nitride, rather than ion sputtering, dominated the etching process, leading to low plasma damage and rough surface morphology. Additionally, to understand the etching-induced surface roughening behaviors, various substrates with different threading dislocation densities were treated at low Pbias. It was found that for the sample (with p-contact size of 10 × 10 μm2), the efficiency droop was approximately 20%, although the current reached 10 mA due most probably to the suppressed polarization effect in the quantum well. It was further observed that the external quantum efficiency (EQE) was dependent on Pbias, where the lowest Pbias yielded the highest maximum EQE, indicating that the plasma damage was mitigated by reducing Pbias. Optimization of dry etching and polarization-suppression conditions could pave the way for realizing high-performance and brightness μLEDs for next-generation displays. DOI: 10.1063/5.0085384 Web of Science Scopus Continuous-wave lasing of AlGaN-based ultraviolet laser diode at 274.8 nm by current injection Zhang, ZY; Kushimoto, M; Yoshikawa, A; Aoto, K; Schowalter, LJ; Sasaoka, C; Amano, H APPLIED PHYSICS EXPRESS 15 巻 ( 4 ) 2022年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Applied Physics Express We demonstrated continuous-wave lasing of an AlGaN-based ultraviolet laser diode, fabricated on a single-crystal AlN substrate when operating at 5 °C. The threshold current density and device series resistance were reduced by improvements to the epitaxial structure and electrode arrangement. A peak wavelength of 274.8 nm was observed for lasing at a drive current over 110 mA, which corresponded to a threshold current density of 3.7 kA cm-2. The operating voltage at the threshold current was as low as 9.6 V. DOI: 10.35848/1882-0786/ac6198 Web of Science Scopus "Regrowth-free" fabrication of high-current-gain AlGaN/GaN heterojunction bipolar transistor with N-p-n configuration Kumabe, T; Watanabe, H; Ando, Y; Tanaka, A; Nitta, S; Honda, Y; Amano, H APPLIED PHYSICS EXPRESS 15 巻 ( 4 ) 2022年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Applied Physics Express An AlGaN/GaN heterojunction bipolar transistor (HBT) with N-p-n configuration was fabricated by the "regrowth-free"method, resulting in a contamination-free emitter-base AlGaN/GaN heterojunction. The low-bias-power-based low-damage inductively coupled plasma-reactive ion etching was employed in this study for emitter mesa definition instead of the conventional selective-area-regrowth technique. The method successfully minimized the etching-induced damage in the p-GaN base layer and the contamination at the emitter-base AlGaN/GaN heterojunction. Consequently, the fabricated device exhibited a high current gain of 25, the highest current density of 15.0 kA cm-2, and the lowest on-state voltage offset of 0.75 V ever reported for AlGaN/GaN HBTs. DOI: 10.35848/1882-0786/ac6197 Web of Science Scopus Mechanism and enhancement of anti-parasitic-reaction catalytic activity of tungsten-carbide-coated graphite components for the growth of bulk GaN crystals Nakamura, D; Iida, K; Horibuchi, K; Aoki, Y; Takahashi, N; Mori, Y; Moriyama, M; Nitta, S; Amano, H APPLIED PHYSICS EXPRESS 15 巻 ( 4 ) 2022年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Applied Physics Express The working mechanism of the anti-parasitic-reaction (APR) catalyst of tungsten carbide (WC) coating on graphite in hydride vapor phase epitaxy GaN growth were examined. During NH3 annealing, the surface of WC is reduced as well as nitrided. The W2N topmost layer was found to work as an APR-active catalyst to suppress the formation of GaN polycrystals during high-rate HVPE-GaN growth, while the regions covered with thick pyrolytic graphite residues were catalytically inert. The formation of an additional W2C top layer on the WC underlayer was demonstrated to exhibit superior APR activity, i.e. complete suppression of GaN polycrystal formation. DOI: 10.35848/1882-0786/ac5ba4 Web of Science Scopus Sputtered polycrystalline MgZnO/Al reflective electrodes for enhanced light emission in AlGaN-based homojunction tunnel junction DUV-LED Matsubara, T; Nagatat, K; Kushimoto, M; Tomai, S; Katsumata, S; Honda, Y; Amano, H APPLIED PHYSICS EXPRESS 15 巻 ( 4 ) 2022年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Applied Physics Express In this study, we enhanced the emission power of AlGaN-based tunnel junction deep-ultraviolet LEDs (TJ LEDs) by using a MgZnO and aluminum stacked structure as UV reflective electrodes on the anode side. The emission wavelength of the fabricated TJ LED was 284 nm, and the emission power was 57.3 mW at 63 A cm-2. The polycrystalline MgZnO enabled both conductivity and UV transmittance to be achieved, approximately doubling with a reflectance of the fabricated TJ LED at 284 nm compared to conventional TJ LED with Ti/Al. These factors contributed to the increased emission power of TJ LEDs. DOI: 10.35848/1882-0786/ac5acf Web of Science Scopus Structural design optimization of 279 nm wavelength AlGaN homojunction tunnel junction deep-UV light-emitting diode Nagata K., Anada S., Miwa H., Matsui S., Boyama S., Saito Y., Kushimoto M., Honda Y., Takeuchi T., Amano H. Applied Physics Express 15 巻 ( 4 ) 2022年4月 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Applied Physics Express We demonstrated the structural optimization of AlGaN tunnel junction (TJ) deep-ultraviolet light-emitting diodes by changing the thickness and impurity concentrations of p+-type and n+-type AlGaN constituting the TJ. By decreasing the total thickness of the TJ to 23 nm, the operating voltage reached a minimum of 8.8 V at 63 A cm-2. Further decrease in TJ thickness markedly increases the operating voltage. This finding implies that the depletion layer width becomes greater than the TJ thickness if it is smaller than 12 nm. Therefore, we conclude that the TJ thickness must be greater than the depletion layer width. DOI: 10.35848/1882-0786/ac60c7 Web of Science Scopus Improved device performance of vertical GaN-on-GaN nanorod Schottky barrier diodes with wet-etching process Liao Y., Chen T., Wang J., Cai W., Ando Y., Yang X., Watanabe H., Tanaka A., Nitta S., Honda Y., Chen K.J., Amano H. Applied Physics Letters 120 巻 ( 12 ) 2022年3月 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Applied Physics Letters In this work, a deliberate etching-based top-down approach is proposed to fabricate the GaN nanorod (NR) Schottky barrier diode (SBD). As a key step during the fabrication, the impact of the wet-etching process on device performance is systematically studied. By virtue of the reduced surface states at the sidewall, the performance of NR SBD with the wet-etching process is substantially improved, delivering a forward turn-on voltage of 0.65 V, a current density of ∼10 kA/cm2 at 3 V, an ideality factor of 1.03, an ON/OFF current ratio of ∼1010, and no severe current collapse, along with a reverse breakdown voltage of 772 V. DOI: 10.1063/5.0083194 Scopus Inhomogeneous Barrier Height Characteristics of n-Type AlInP for Red AlGaInP-Based Light-Emitting Diodes Cha, JS; Lee, DH; Sim, KB; Lee, TJ; Seong, TY; Amano, H ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY 11 巻 ( 3 ) 2022年3月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:ECS Journal of Solid State Science and Technology For micro-light-emitting diode (LED)-based display applications, such as virtual reality and augmented reality, high-performance Ohmic contacts (namely, the improvement of current injection efficiency) is vital to the realization of high-efficiency micro-LEDs. The surface Fermi level pinning characteristics could be comprehended in terms of the relation between work function of metals (M) and Schottky barrier height (SBH, B). In this study, we have investigated the surface Fermi level pinning characteristics of (001) n-AlInP surfaces by employing Schottky diodes with different metals. With an increase in the temperature, B increases linearly and ideality factors (n) decreases. This behavior is related to the barrier height inhomogeneity. Inhomogeneity-modelbased B is evaluated to be in the range of 0.86 1.30 eV, which is dependent on the metal work functions and are similar to those measured from capacitance-voltage relation. Further, The S-parameter, the relation between B and M (d B/d M), is 0.36. This is indicative of the partial pinning of the surface Fermi level at the surface states placed at 0.95 eV below the conduction band. Furthermore, it is also shown that (NH4)2S-passivation results in an increases the mean SBH and the S-parameter (e.g., 0.52). DOI: 10.1149/2162-8777/ac5d66 Web of Science Scopus Visualization of depletion layer in AlGaN homojunction p-n junction Nagata, K; Anada, S; Saito, Y; Kushimoto, M; Honda, Y; Takeuchi, T; Yamamoto, K; Hirayama, T; Amano, H APPLIED PHYSICS EXPRESS 15 巻 ( 3 ) 2022年3月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Applied Physics Express We analyzed the p-n junction of an aluminum gallium nitride (AlGaN) homojunction tunnel junction (TJ) deep-ultraviolet light-emitting diode by phase-shifting electron holography. We clearly obtained a phase image reflecting the band alinement of the p-n homojunction and derived a depletion layer width of approximately 10 nm. In addition, the observed depletion layer width for the AlGaN TJ was in good agreement with the simulated one reflecting the diffusion profile of Mg and Si, thus enabling a discussion on the electrical conduction mechanism for an AlGaN p-n junction. DOI: 10.35848/1882-0786/ac53e2 Web of Science Scopus Effect of beam current on defect formation by high-temperature implantation of Mg ions into GaN Itoh, Y; Watanabe, H; Ando, Y; Kano, E; Deki, M; Nitta, S; Honda, Y; Tanaka, A; Ikarashi, N; Amano, H APPLIED PHYSICS EXPRESS 15 巻 ( 2 ) 2022年2月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Applied Physics Express We evaluated the beam current dependence of defect formation during Mg ion implantation into GaN at a high temperature of 1100 °C with two beam currents. Photoluminescence spectra suggest that low-beam-current implantation reduced the vacancy concentration and activated Mg to a greater extent. Moreover, scanning transmission electron microscopy analysis showed that low-beam-current implantation reduced the density of Mg segregation defects with inactive Mg and increased the density of intrinsic dislocation loops, suggesting decreases in the densities of Ga and N vacancies. The formation of these defects depended on beam current, which is an important parameter for defect suppression. DOI: 10.35848/1882-0786/ac481b Web of Science Scopus Defect characterization of { 10 1 ¯ 3 } GaN by electron microscopy Kusch G., Frentrup M., Hu N., Amano H., Oliver R.A., Pristovsek M. Journal of Applied Physics 131 巻 ( 3 ) 2022年1月 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Journal of Applied Physics Advances in obtaining untwinned (10 1 ¯3)-oriented semi-polar GaN enable a new crystal orientation for the growth of green and red LED structures. We present a scanning electron microscopy study that combines the structural characterization of electron channeling contrast imaging with the optical characterization of cathodoluminescence hyperspectral imaging on a (10 1 ¯ 3) GaN layer. An extensive defect analysis revealed that the dominant defects consist of basal plane stacking faults (BSFs), prismatic stacking faults, partial dislocations, and threading dislocations. With a defect density of about an order of magnitude lower than in comparable. The optical properties of the defects have been characterized from 10 to 320 K, showing BSF luminescence at room temperature indicating a reduced density of non-radiative recombination centers in the as-grown samples compared to established semi- and non-polar orientations. Our findings suggest that growth along (10 1 ¯3) has the potential for higher radiative efficiency than established semi-polar orientations. DOI: 10.1063/5.0077084 Scopus Perspective on thermal conductance across heterogeneously integrated interfaces for wide and ultrawide bandgap electronics Cheng, Z; Graham, S; Amano, H; Cahill, DG APPLIED PHYSICS LETTERS 120 巻 ( 3 ) 2022年1月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Applied Physics Letters Heterogeneous integration is important to create multi-functionality in future electronic devices. However, few thermal studies of the interfaces formed in these integrated devices have been reported before. Recently, integrated interfaces by surface-Activated bonding were found to have high thermal boundary conductance, which provides a solution for heat dissipation of GaN and β-Ga2O3-based power electronics. Here, we review the recent progress on the interfacial thermal transport across heterogeneously integrated interfaces, including transferred van der Waals force bonded interfaces, surface-Activated bonded interfaces, plasma bonded interfaces, and hydrophilic bonded interfaces. This Perspective specifically focuses on applications of thermal management strategies of electronics, especially power electronics. Finally, the challenges, such as high-Throughput thermal measurements of buried interfaces, thermal property-structure relations of interfaces bonded under different conditions, theoretical understanding of interfacial thermal transport, and device demonstrations, are pointed out. DOI: 10.1063/5.0077039 Web of Science Scopus Threshold increase and lasing inhibition due to hexagonal-pyramid-shaped hillocks in AlGaN-based DUV laser diodes on single-crystal AlN substrate Kushimoto, M; Zhang, ZY; Honda, Y; Schowalter, LJ; Sasaoka, C; Amano, H JAPANESE JOURNAL OF APPLIED PHYSICS 61 巻 ( 1 ) 2022年1月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Japanese Journal of Applied Physics The presence of hexagonal-pyramid-shaped hillocks (HPHs) in AlGaN epitaxial films affects device characteristics; this effect is significant in DUV laser diodes (LDs) on AlN substrates, where the presence of HPHs under the p-electrode increases the threshold current density and inhibits the lasing. In this study, we investigated the difference between the lasing characteristics of LDs with and without HPHs. It was found that in the presence of HPHs, the threshold excitation power density increased and the slope efficiency decreased by optical excitation. To investigate the cause of these phenomena, we performed structural, optical, and electrical analyses of the HPHs. Various imaging techniques were used to directly capture the characteristics of the HPHs. As a result, we concluded that HPHs cause the degradation of LD characteristics due to a combination of structural, optical, and electrical factors. DOI: 10.35848/1347-4065/ac3a1d Web of Science Scopus Ohmic Contact to p-Type GaN Enabled by Post-Growth Diffusion of Magnesium Wang, J; Lu, S; Cai, WT; Kumabe, T; Ando, Y; Liao, YQ; Honda, Y; Xie, YH; Amano, H IEEE ELECTRON DEVICE LETTERS 43 巻 ( 1 ) 頁: 150 - 153 2022年1月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:IEEE Electron Device Letters We demonstrated the formation of excellent Ohmic contact to p-type GaN (including the plasma etching-damaged p-type GaN which otherwise exhibited undetectable current within ±5 V) by the post-growth diffusion of magnesium. The specific contact resistivity on the order of 10-4Omega cm2 (extracted at V=0 V) was achieved on the plasma-damaged p-GaN with linear current-voltage characteristics by the transfer length method (TLM) measurement. The improvement in current by a factor of over 109 was also obtained on the plasma-damaged p-n junction diode after the same Mg-treatment. These experimental results indicate a great potential of post-growth diffusion of Mg to overcome the bottleneck of forming a good Ohmic contact to p-GaN. DOI: 10.1109/LED.2021.3131057 Web of Science Scopus Frontier electronics in memory of Professor Isamu Akasaki Amano, H GALLIUM NITRIDE MATERIALS AND DEVICES XVII 12001 巻 2022年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Proceedings of SPIE - The International Society for Optical Engineering ISAMU AKASAKI, crystal grower, a pioneer of GaN-based blue light-emitting diodes (LEDs), and a Nobel Laureate in Physics, passed away because of pneumonia on April 1, 2021 at the age of 92. According to the Nobel Foundation, the LED lamp holds considerable promise for improving the quality of life of over 1.5 billion people worldwide who lack access to electricity grids. Owing to its low power requirements, it can be powered by cheap local solar energy. In this article, his pursuit of blue LEDs for 20 years is described. DOI: 10.1117/12.2619005 Web of Science Scopus An Accurate Approach to Develop Small Signal Circuit Models for AlGaN/GaN HEMTs Using Rational Functions and Dependent Current Sources Jadhav, A; Ozawa, T; Baratov, A; Asubar, JT; Kuzuhara, M; Wakejima, A; Yamashita, S; Deki, M; Nitta, S; Honda, Y; Amano, H; Roy, S; Sarkar, B IEEE JOURNAL OF THE ELECTRON DEVICES SOCIETY 10 巻 頁: 797 - 807 2022年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:IEEE Journal of the Electron Devices Society In this paper, a technique to develop small signal circuit (SSC) models of AlGaN/GaN high electron mobility transistors (HEMTs) using dependent current sources is presented. In this technique, experimentally measured broadband Y-parameters of AlGaN/GaN HEMTs are mathematically modeled as a sum of pole-residue terms. By representing each pole-residue term as a dependent current source, it is possible to develop an accurate SSC models for HEMTs which otherwise may not be possible using passive resistive-inductive-capacitive elements. The accuracy of the proposed SSC model is validated against the conventional SSC model using a 2nd, 3rd and 4th order rational function representation of the admittance branches of AlGaN/GaN HEMTs. Therefore, the proposed SSC model turns out to be highly robust in nature and can take care of any form of the transfer functions of the admittance branches between the gate, drain, and source terminal of an AlGaN/GaN HEMT. DOI: 10.1109/JEDS.2022.3208028 Web of Science Scopus Promising Results of National Project by Japanese Ministry of the Environment to Develop GaN on GaN Power Devices and Prove their Usefulness in Real Systems Otoki Y., Shibata M., Mishima T., Ohta H., Mori Y., Imanishi M., Tamura S., Kidera K., Takino J., Okayama Y., Watanabe K., Okamoto N., Honda Y., Yamamoto M., Shiozaki K., Amano H. 2022 International Conference on Compound Semiconductor Manufacturing Technology, CS MANTECH 2022 頁: 237 - 242 2022年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:2022 International Conference on Compound Semiconductor Manufacturing Technology, CS MANTECH 2022 Exciting high performance power electronic devices have been widely demonstrated and manufactured using GaN epitaxial layers, but the majority of these devices have been fabricated on lattice mismatched substrates, including SiC, Si, or sapphire. Unfortunately, using lattice mismatched substrates inevitably introduces high concentrations of point defects and dislocations into the GaN epilayers, and these defects degrade the electrical performance of the fabricated GaN devices. Also, the mismatch of lattice constant and coefficient of thermal expansion cause strain and wafer bowing in the GaN epi, which further degrade the quality material for device fabrication. Using lattice matched GaN substrates provides solutions to these problems. In 2014, the Ministry of the Environment launched a national project to develop the required technology and to prove the superiority of GaN on GaN devices in real systems, with more than 10 partnerships from academia and industry. The project included work in several areas, including GaN substrate growth, GaN epitaxy, material characterization, and fabrication of devices and ICs for application in various systems. Large area GaN substrates have been grown with low defect densities, which has enabled fabrication of new types of vertical and horizontal GaN devices. The GaN devices have been used in servers, solar cell power conditioners, microwave ICs, distribution transformers, electric vehicle power converters. The performance improvements were compared with conventional approaches in each case. An “ALL GaN vehicle” has also been demonstrated, in which GaN devices are used in all power components. In this talk, we will present these results which show the great potential of GaN on GaN devices in the industry. Scopus 深紫外線LEDを搭載したつづら折り流路を通過するウイルスの壁面付着および不活化性能 高牟礼 光太郎, 岩谷 靖雅, 坂本 恭晃, 八木 哲也, 天野 浩, 内山 知実 年次大会 2022 巻 ( 0 ) 頁: S055-11 2022年 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:一般社団法人 日本機械学会 DOI: 10.1299/jsmemecj.2022.s055-11 CiNii Research 呼気中のエアロゾルを遮断するデスクトップ型エアカーテン装置の開発 高牟礼 光太郎, 坂本 恭晃, 八木 哲也, 岩谷 靖雅, 天野 浩, 内山 知実 年次大会 2022 巻 ( 0 ) 頁: S055-10 2022年 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:一般社団法人 日本機械学会 DOI: 10.1299/jsmemecj.2022.s055-10 CiNii Research 卓上型エアカーテン装置によるエアロゾル粒子の遮断および捕集性能 高牟礼 光太郎, 小林 大亮, 武藤 広将, 春木 健杜, 天野 浩, 八木 哲也, 岩谷 靖雅, 内山 知実 流体工学部門講演会講演論文集 2022 巻 ( 0 ) 頁: OS03-22 2022年 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:一般社団法人 日本機械学会 DOI: 10.1299/jsmefed.2022.os03-22 CiNii Research Ohmic contact on low-doping-density p-type GaN with nitrogen-annealed Mg Lu, S; Deki, M; Wang, J; Ohnishi, K; Ando, Y; Kumabe, T; Watanabe, H; Nitta, S; Honda, Y; Amano, H APPLIED PHYSICS LETTERS 119 巻 ( 24 ) 2021年12月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Applied Physics Letters We have demonstrated a fabrication process for the Ohmic contact on low-doping-density p-type GaN with nitrogen-annealed Mg. An Ohmic contact with a contact resistance of 0.158 ω cm2 is realized on p-GaN ([Mg] = 1.3 × 1017 cm-3). The contact resistance of p-type GaN with higher Mg concentration ([Mg]=1.0 × 1019 cm-3) can also be reduced to 2.8 × 10-5 ω cm2. A localized contact layer is realized without any etching or regrowth damage. The mechanism underlying this reduced contact resistance is studied by scanning transmission electron microscopy with energy dispersive x-ray spectroscopy and secondary ion mass spectrometry, representing a mutual diffusion of Ga and Mg atoms on the interface. Reductions in the barrier height and surface depletion width with the nitrogen-annealed Mg layer are confirmed by XPS and Hall effect measurements qualitatively. DOI: 10.1063/5.0076764 Web of Science Scopus Uniting a III-Nitride Transmitter, Waveguide, Modulator, and Receiver on a Single Chip Xie, MY; Jiang, Y; Gao, XM; Cai, W; Yuan, JL; Zhu, HB; Wang, YJ; Zeng, XF; Zhang, ZY; Liu, YH; Amano, H ADVANCED ENGINEERING MATERIALS 23 巻 ( 12 ) 2021年12月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Advanced Engineering Materials The integration of III-nitride electronics and photonics is of great interest toward future computing systems with low power consumption. Multifunctioning multiple quantum well (MQW) diodes can address the challenging issue for on-chip integration of a light source, which is a key component to drive the photonic circuits. Herein, a transmitter, waveguide, modulator, and receiver are monolithically integrated on a III-nitride-on-silicon platform to perform light emission, transmission, modulation, and detection simultaneously. Both the receiver and modulator exhibit sufficient sensitivity to optical signals from the transmitter, which has an identical InGaN/AlGaN multiple quantum well (MQW) structure because the III-nitride diode provides spectral overlap between the emission and absorption spectra. On-chip data communication among these optical components is achieved using light, and the effective wavelength range is from 365 to 385 nm, in which multifunctional devices can be operated. DOI: 10.1002/adem.202100582 Web of Science Scopus Discrete wavelengths observed in electroluminescence originating from Al追悼
赤﨑 勇先生を偲んで
DOI: 10.11316/butsuri.76.7_478 CiNii Research Vertical GaN-on-GaN nanowire Schottky barrier diodes by top-down fabrication approach Liao Y., Chen T., Wang J., Ando Y., Cai W., Yang X., Watanabe H., Hirotani J., Tanaka A., Nitta S., Honda Y., Chen K.J., Amano H. Japanese Journal of Applied Physics 60 巻 ( 7 ) 2021年7月 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Japanese Journal of Applied Physics An optimized top-down approach was utilized to fabricate vertical GaN-on-GaN nanowire Schottky barrier diodes (NWSBDs) in this letter. The suppressed reverse leakage current and enhanced breakdown voltage (BV) of the vertical GaN NWSBDs are attributed to the reduced electric field at the interface of the Schottky junction achieved through the dielectric reduced surface field technique. As-fabricated NWSBD delivers a low turn-on voltage of 0.80 V, a near-unity ideality factor of 1.04, along with a soft BV of 480 V. The measured soft BV is comparable with the avalanche BV of the p-n diode with a similar net doping concentration in the drift region. DOI: 10.35848/1347-4065/ac06b5 Web of Science Scopus Isamu Akasaki: The Pioneer of Blue LEDs and his Collaboration with pss OBITUARY Amano, H PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE 218 巻 ( 14 ) 2021年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1002/pssa.202100329 Web of Science Non-polar true-lateral GaN power diodes on foreign substrates Wang, J; Yu, G; Zong, H; Liao, YQ; Lu, WF; Cai, WT; Hu, XD; Xie, YH; Amano, H APPLIED PHYSICS LETTERS 118 巻 ( 21 ) 2021年5月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Applied Physics Letters We have demonstrated non-polar GaN power diodes (Schottky barrier diode and p-n junction diode) on foreign substrates featuring the true-lateral p-n and metal-semiconductor junctions. The diodes were fabricated on GaN islands laterally overgrown on the mask-patterned sapphire and Si substrates by metalorganic vapor phase epitaxy. The anode and cathode were formed on the opposed a-plane sidewalls of the island, making the device architecture essentially like the 90° rotation of the desired true-vertical power diodes. The ideality factor of the Schottky barrier diode remained 1.0 (from 1.00 to 1.05) over 7 decades in current. Specifically, a high critical electric field of 3.3 MV/cm was demonstrated on the p-n junction diode with avalanche capability. These performances reveal a strong potential of non-polar GaN with the true-lateral junctions for high power applications. DOI: 10.1063/5.0051552 Web of Science Scopus The stability of graphene and boron nitride for III-nitride epitaxy and post-growth exfoliation. Park JH, Yang X, Lee JY, Park MD, Bae SY, Pristovsek M, Amano H, Lee DS Chemical science 12 巻 ( 22 ) 頁: 7713 - 7719 2021年5月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Chemical Science A challenging approach, but one providing a key solution to material growth, remote epitaxy (RE)—a novel concept related to van der Waals epitaxy (vdWE)—requires the stability of a two-dimensional (2-D) material. However, when graphene, a representative 2-D material, is present on substrates that have a nitrogen atom, graphene loss occurs. Although this phenomenon has remained a hurdle for over a decade, restricting the advantages of applying graphene in the growth of III-nitride materials, few previous studies have been conducted. Here, we report the stability of graphene on substrates containing oxygen or nitrogen atoms. Graphene has been observed on highly decomposed Al2O3; however, graphene loss occurred on decomposed AlN at temperatures over 1300 °C. To overcome graphene loss, we investigated 2-D hexagonal boron nitride (h-BN) as an alternative. Unlike graphene on AlN, it was confirmed that h-BN on AlN was intact after the same high-temperature process. Moreover, the overgrown AlN layers on both h-BN/AlN and h-BN/Al2O3could be successfully exfoliated, which indicates that 2-D h-BN survived after AlN growth and underlines its availability for the vdWE/RE of III-nitrides with further mechanical transfer. By enhancing the stability of the 2-D material on the substrate, our study provides insights into the realization of a novel epitaxy concept. DOI: 10.1039/d1sc01642c Web of Science Scopus PubMed Etching-induced damage in heavily Mg-doped p-type GaN and its suppression by low-bias-power inductively coupled plasma-reactive ion etching Kumabe, T; Ando, Y; Watanabe, H; Deki, M; Tanaka, A; Nitta, S; Honda, Y; Amano, H JAPANESE JOURNAL OF APPLIED PHYSICS 60 巻 ( SB ) 頁: SBBD03 2021年5月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Japanese Journal of Applied Physics Inductively coupled plasma–reactive ion etching (ICP–RIE)-induced damage in heavily Mg-doped p-type GaN ([Mg] = 2 × 1019 cm−3) was investigated by low-temperature photoluminescence (PL) and depth-resolved cathodoluminescence (CL) spectroscopy. From PL measurements, we found broad yellow luminescence (YL) with a maximum at around 2.2–2.3 eV, whose origin was considered to be isolated nitrogen vacancies (VN), only in etched samples. The depth-resolved CL spectroscopy revealed that the etching-induced YL was distributed up to the electron-beam penetration depth of around 200 nm at a high ICP–RIE bias power (Pbias). Low-bias-power (low-Pbias) ICP–RIE suppressed the YL and its depth distribution to levels similar to those of an unetched sample, and a current–voltage characteristic comparable to that of an unetched sample was obtained for a sample etched with Pbias of 2.5 W. DOI: 10.35848/1347-4065/abd538 Web of Science Scopus Impact of heat treatment process on threshold current density in AlGaN-based deep-ultraviolet laser diodes on AlN substrate Kushimoto, M; Zhang, ZY; Sugiyama, N; Honda, Y; Schowalter, LJ; Sasaoka, C; Amano, H APPLIED PHYSICS EXPRESS 14 巻 ( 5 ) 頁: 051003 2021年5月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Applied Physics Express The electroluminescence (EL) uniformity of AlGaN-based deep UV laser diodes on AlN substrate was analyzed by using the EL imaging technique. Although nonuniform EL patterns were observed, the uniformity was improved by changing the position of the p-electrode. The threshold current density was also reduced by suppressing the inhomogeneity of the EL. Cathodoluminescence analysis revealed that the cause of the non-uniformity is the degradation of the active layer and the nonuniformity emission formed by rapid thermal annealing at high temperature after mesa structure formation. DOI: 10.35848/1882-0786/abf443 Web of Science Scopus Micro-Light Emitting Diode: From Chips to Applications Parbrook, PJ; Corbett, B; Han, J; Seong, TY; Amano, H LASER & PHOTONICS REVIEWS 15 巻 ( 5 ) 頁: 2000133 2021年5月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Laser and Photonics Reviews Typical light-emitting diodes (LEDs) have a form factor >(300 × 300) µm2. Such LEDs are commercially mature in illumination and ultralarge displays. However, recent LED research includes shrinking individual LED sizes from side lengths >300 µm to values <100 µm, leading to devices called micro-LEDs. Their advent creates a number of exciting new application spaces. Here, a review of the principles and applications of micro-LED technology is presented. In particular, the implications of reduced LED size in necessitating mitigation strategies for nonradiative device edge damage as well as the potential for higher drive current densities are discussed. The opportunities to integrate micro-LEDs with electronics, and into large-scale arrays, allow pixel addressable scalable integrated displays, while the small micro-LED size is ideal for high-speed modulation for visible light communication, and for integration into biological systems as part of optogenetic therapies. DOI: 10.1002/lpor.202000133 Web of Science Scopus Discrete AlN mole fraction of n/12 (n = 4-8) in Ga-rich zones functioning as electron pathways created in nonflat AlGaN layers grown on high-miscut sapphire substrates Nagasawa Y., Hirano A., Ippommatsu M., Sako H., Hashimoto A., Sugie R., Honda Y., Amano H., Akasaki I., Kojima K., Chichibu S.F. Journal of Applied Physics 129 巻 ( 16 ) 頁: 164503 2021年4月 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Journal of Applied Physics Ga-rich zones created along macrosteps in n-AlGaN plausibly function as electron pathways of AlGaN-based deep-ultraviolet (DUV) LEDs fabricated on AlN templates using 1.0°-miscut c(0001) sapphire substrates toward the m[1-100] axis. This work was performed to clarify AlN mole fractions (xAl) of Ga-rich zones. xAl ≃ (7/12, 6/12, and 5/12) was observed in Ga-rich zones in AlαGa1−αN (α ≃ 0.63, 0.55, and 0.43, respectively) by the method proposed in our previous article in which we showed that Ga-rich zones of Al8/12Ga4/12N were created in Al0.7Ga0.3N. xAl in the Ga-rich zones obtained from an energy-dispersive x-ray signal by scanning transmission electron microscopy calibrated by Rutherford backscattering well agreed with xAl obtained by cross-sectional cathodoluminescence (CL) spectroscopy using scanning electron microscopy. A weak CL shoulder peak corresponding to Al4/12Ga8/12N was also observed for Al0.43Ga0.57N. In addition, xAl ≃ n/12 (n = 6-9) in Al-rich zones appeared in the rest of the Ga-rich zones. Furthermore, nanobeam electron diffraction patterns of the Ga-rich zones indicated a high possibility of a regular configuration of Ga and Al atoms on the c(0001) plane in our samples. Consequently, xAl values in nonflat AlGaN layers with macrosteps were often determined to be near n/12 (n: integer). Thus, Ga-rich zones (xAl = n/12: n = 4-8) formed in our nonflat AlGaN layers, which originated from the macrosteps along [11-20] edgelines normal to the m[1-100] axis, are suggested to be metastable. The creation of discrete xAl in Ga-rich zones should contribute to the stable production of DUV-LEDs using high-miscut sapphire substrates. DOI: 10.1063/5.0042036 Web of Science Scopus Experimental demonstration of GaN IMPATT diode at X-band Kawasaki, S; Ando, Y; Deki, M; Watanabe, H; Tanaka, A; Nitta, S; Honda, Y; Arai, M; Amano, H APPLIED PHYSICS EXPRESS 14 巻 ( 4 ) 頁: 046501 2021年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Applied Physics Express We report the first experimental demonstration of microwave oscillation in GaN impact ionization avalanche time transit (IMPATT) diodes at the X-band. The device used in this study is a single drift diode with a p+–n simple abrupt junction and vertical mesa termination. The reverse I–V characteristic of the diode shows low leakage current, clear avalanche breakdown, and high avalanche capability, as required for IMPATT operation. Microwave testing is performed in an X-band waveguide circuit with a reduced-height waveguide resonant cavity. Oscillations are observed at 9.52 GHz at a power of ∼56 mW. DOI: 10.35848/1882-0786/abe3dc Web of Science Scopus Optimization of Ni/Ag-Based Reflectors to Improve the Performance of 273 nm Deep Ultraviolet AlGaN-Based Light Emitting Diodes Sim, KB; Kim, SK; Lee, HS; Lee, SY; Seong, TY; Amano, H ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY 10 巻 ( 4 ) 頁: 045005 2021年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:ECS Journal of Solid State Science and Technology We optimized Ni/Ag-based p-type reflectors for the improvement of efficiency of 273 nm deep ultraviolet (DUV) AlGaN-based flip-chip light emitting diodes (FCLEDs). The Ni(3 nm)/Ag(5-15 nm)/Al/Ni and Ni(25-50 nm)/Ag/Ni contacts exhibited higher reflectance (36.4-39.5%) at 273 nm than reference Ni(5 nm)/Au(5 nm)/Al/Ni contact (26.1%). The Ni(3 nm)/Ag/Al(200 nm)/Ni(20 nm) and Ni/Ag(200 nm)/Ni(20 nm)-based FCLEDs gave forward voltages in the rage of 6.93-7.11 V and 5.5-6.28 V at 20 mA, respectively, whereas the Ni/Au-based sample showed 6.35 V. Further, the Ni(3 nm)/Ag(10 nm)/Al/Ni-based and Ni(50 nm)/Ag(200 nm)/Ni-based samples exhibited 4.85% and 13.4% larger output power at 1.2 W than the reference sample. The Ni(3 nm)/Ag(10 nm)-based and Ni(50 nm)/Ag(200 nm)/Ni-based samples produced 5.6% and 8.5% higher peak external quantum efficiency than the reference sample. It was further shown that the Ni(3 nm)/Ag(10 nm)/Al/Ni-based and Ni(50 nm)/Ag(200 nm)/Ni-based samples experienced less efficiency droop (namely, 27.9 and 26.4%, respectively) than the reference sample (31.4%). Based on the scanning transmission electron microscopy and X-ray photoemission spectroscopy results, the ohmic formation mechanism is described and discussed. DOI: 10.1149/2162-8777/abf49b Web of Science Scopus Numerical Simulation of Ammonothermal Crystal Growth of GaN-Current State, Challenges, and Prospects Schimmel, S; Tomida, D; Ishiguro, T; Honda, Y; Chichibu, S; Amano, H CRYSTALS 11 巻 ( 4 ) 頁: 356 2021年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Crystals Numerical simulations are a valuable tool for the design and optimization of crystal growth processes because experimental investigations are expensive and access to internal parameters is limited. These technical limitations are particularly large for ammonothermal growth of bulk GaN, an important semiconductor material. This review presents an overview of the literature on simulations targeting ammonothermal growth of GaN. Approaches for validation are also reviewed, and an overview of available methods and data is given. Fluid flow is likely in the transitional range between laminar and turbulent; however, the time-averaged flow patterns likely tend to be stable. Thermal boundary conditions both in experimental and numerical research deserve more detailed evaluation, especially when designing numerical or physical models of the ammonothermal growth system. A key source of uncertainty for calculations is fluid properties under the specific conditions. This originates from their importance not only in numerical simulations but also in designing similar physical model systems and in guiding the selection of the flow model. Due to the various sources of uncertainty, a closer integration of numerical modeling, physical modeling, and the use of measurements under ammonothermal process conditions appear to be necessary for developing numerical models of defined accuracy. DOI: 10.3390/cryst11040356 Web of Science Scopus Strain-induced yellow to blue emission tailoring of axial InGaN/GaN quantum wells in GaN nanorods synthesized by nanoimprint lithography Avit, G; Robin, Y; Liao, YQ; Nan, H; Pristovsek, M; Amano, H SCIENTIFIC REPORTS 11 巻 ( 1 ) 頁: 6754 2021年3月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Scientific Reports GaN nanorods (NRds) with axial InGaN/GaN MQWs insertions are synthesized by an original cost-effective and large-scale nanoimprint-lithography process from an InGaN/GaN MQWs layer grown on c-sapphire substrates. By design, such NRds exhibit a single emission due to the c-axis MQWs. A systematic study of the emission of the NRds by time-resolved luminescence (TR-PL) and power dependence PL shows a diameter-controlled luminescence without significant degradation of the recombination rate thanks to the diameter-controlled strain tuning and QSCE. A blueshift up to 0.26 eV from 2.28 to 2.54 eV (543 nm to 488 nm) is observed for 3.2 nm thick InGaN/GaN QWs with an In composition of 19% when the NRds radius is reduced from 650 to 80 nm. The results are consistent with a 1-D based strain relaxation model. By combining state of the art knowledge of c-axis growth and the strong strain relieving capability of NRds, this process enables multiple and independent single-color emission from a single uniform InGaN/GaN MQWs layer in a single patterning step, then solving color mixing issue in InGaN based nanorods LED devices. DOI: 10.1038/s41598-021-86139-9 Web of Science Scopus PubMed Progress in Modeling Compound Semiconductor Epitaxy: Unintentional Doping in GaN MOVPE Kangawa, Y; Kusaba, A; Kempisty, P; Shiraishi, K; Nitta, S; Amano, H CRYSTAL GROWTH & DESIGN 21 巻 ( 3 ) 頁: 1878 - 1890 2021年3月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Crystal Growth and Design To improve the properties of semiconductors, it is necessary to construct an integrated crystal growth model that covers all elementary processes of metal-organic vapor phase epitaxy (MOVPE). Although there are several theoretical models that can reproduce any elemental growth process, they are inadequate for controlling semiconductor epitaxy: the elementary processes of (1) the vapor phase reaction, (2) the surface reaction, and (3) incorporation are entangled with each other. That is, sequential analyses of elementary growth processes from upstream (1) to downstream (3) are indispensable for an understanding of the entire process of MOVPE. In this Review, the recent progress of theoretical models based on calculations from first-principles calculations are summarized. The possibility of predicting carbon concentrations in GaN grown by MOVPE are explored as an example. The results of calculations using a model that integrates (1) → (2) → (3) reproduce the experimental tendencies of carbon incorporation. Calculations show that the contribution of each elementary growth process to a change in carbon concentration can be discussed separately, but the relationship between the input parameters and the resulting outputs can only be determined through experiment. Although this examination explores a special case, the development of a precise integrated crystal growth model would greatly contribute to innovation in semiconductor manufacturing. DOI: 10.1021/acs.cgd.0c01564 Web of Science Scopus Fabrication of GaN cantilever on GaN substrate by photo-electrochemical etching Yamada, T; Ando, Y; Watanabe, H; Furusawa, Y; Tanaka, A; Deki, M; Nitta, S; Honda, Y; Suda, J; Amano, H APPLIED PHYSICS EXPRESS 14 巻 ( 3 ) 頁: 036505 2021年3月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Applied Physics Express Photo-electrochemical (PEC) etching is a promising technique for fabricating GaN microelectromechanical systems devices. In this study, we demonstrate the fabrication of GaN cantilevers by the bandgap-selective PEC etching of an InGaN superlattice sacrificial layer. By using an InGaN superlattice as a sacrifice layer, we found the PEC etching rate became higher than using a normal InGaN layer. As a result, the InGaN superlattice was completely etched and we fabricated GaN-based cantilevers whose resonance characteristics were measured. The Young’s modulus of GaN was determined from the resonance characteristics of GaN cantilevers to be the same as the highest value reported previously. DOI: 10.35848/1882-0786/abe657 Web of Science Scopus Boundary Conditions for Simulations of Fluid Flow and Temperature Field during Ammonothermal Crystal Growth-A Machine-Learning Assisted Study of Autoclave Wall Temperature Distribution Schimmel Saskia, Tomida Daisuke, Saito Makoto, Bao Quanxi, Ishiguro Toru, Honda Yoshio, Chichibu Shigefusa, Amano Hiroshi CRYSTALS 11 巻 ( 3 ) 頁: 1 - 27 2021年3月 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Crystals Thermal boundary conditions for numerical simulations of ammonothermal GaN crystal growth are investigated. A global heat transfer model that includes the furnace and its surroundings is presented, in which fluid flow and thermal field are treated as conjugate in order to fully account for convective heat transfer. The effects of laminar and turbulent flow are analyzed, as well as those of typically simultaneously present solids inside the autoclave (nutrient, baffle, and multiple seeds). This model uses heater powers as a boundary condition. Machine learning is applied to efficiently determine the power boundary conditions needed to obtain set temperatures at specified locations. Typical thermal losses are analyzed regarding their effects on the temperature distribution inside the autoclave and within the autoclave walls. This is of relevance because autoclave wall temperatures are a convenient choice for setting boundary conditions for simulations of reduced domain size. Based on the determined outer wall temperature distribution, a simplified model containing only the autoclave is also presented. The results are compared to those observed using heater-long fixed temperatures as boundary condition. Significant deviations are found especially in the upper zone of the autoclave due to the important role of heat losses through the autoclave head. DOI: 10.3390/cryst11030254 Web of Science Scopus Development of Pulsed TEM Equipped with Nitride Semiconductor Photocathode for High-Speed Observation and Material Nanofabrication Yasuda, H; Nishitani, T; Ichikawa, S; Hatanaka, S; Honda, Y; Amano, H QUANTUM BEAM SCIENCE 5 巻 ( 1 ) 頁: 5 2021年3月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Quantum Beam Science The development of pulsed electron sources is applied to electron microscopes or electron beam lithography and is effective in expanding the functions of such devices. The laser photocathode can generate short pulsed electrons with high emittance, and the emittance can be increased by changing the cathode substrate from a metal to compound semiconductor. Among the substrates, nitride-based semiconductors with a negative electron affinity (NEA) have good advantages in terms of vacuum environment and cathode lifetime. In the present study, we report the development of a photocathode electron gun that utilizes photoelectron emission from a NEA-InGaN substrate by pulsed laser excitation, and the purpose is to apply it to material nanofabrication and high-speed observation using a pulsed transmission electron microscope (TEM) equipped with it. DOI: 10.3390/qubs5010005 Web of Science Scopus Suppression of the regrowth interface leakage current in AlGaN/GaN HEMTs by unactivated Mg doped GaN layer Liu, T; Watanabe, H; Nitta, S; Wang, J; Yu, G; Ando, Y; Honda, Y; Amano, H; Tanaka, A; Koide, Y APPLIED PHYSICS LETTERS 118 巻 ( 7 ) 頁: 072103 2021年2月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Applied Physics Letters The leakage current caused by the Si pileup at the regrowth interface of AlGaN/GaN high electron mobility transistors (HEMTs) is significantly suppressed by the semi-insulating Mg-doped GaN layer. Mg is unintentionally doped and can be originated from the graphite susceptor of metal organic vapor phase epitaxy. Before regrowth of the AlGaN/GaN heterostructure, the GaN template is treated with hydrochloric acid (HCl) and hydrogen peroxide/potassium hydroxide (H2O2/KOH) solution to promote the adsorption of Mg on the GaN surface. The Mg-doped GaN channel layer is highly resistive due to the passivation of hydrogen. The p-n junction formed by the weakly p-type Mg-doped GaN layer and the n-type Si pileup layer depletes the excess electrons at the regrowth interface. As a result, the off-state drain leakage current of the HEMT device can be decreased by two orders of magnitude at 40 V. DOI: 10.1063/5.0034584 Web of Science Scopus Optical properties of neodymium ions in nanoscale regions of gallium nitride (vol 10, pg 2614, 2020) Sato, SI; Deki, M; Watanabe, H; Nitta, S; Honda, Y; Nishimura, T; Gibson, BC; Greentree, AD; Amano, H; Ohshima, T OPTICAL MATERIALS EXPRESS 11 巻 ( 2 ) 頁: 524 - 524 2021年2月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Optical Materials Express We correct an error in the Eq. (1). DOI: 10.1364/OME.420328 Web of Science Scopus 3D GaN Power Switching Electronics: A Revival of Interest in ELO Wang, J; Amano, H; Xie, YH 2021 5TH IEEE ELECTRON DEVICES TECHNOLOGY & MANUFACTURING CONFERENCE (EDTM) 2021年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:2021 5th IEEE Electron Devices Technology and Manufacturing Conference, EDTM 2021 We reported the first-time utilization of ELO (epitaxial lateral overgrowth) GaN (gallium nitride) for power diodes. The undesired stage of coalescence related to ELO is avoided by virtue of a novel 3D device architecture built on the ELO GaN islands on foreign substrate which features pure-lateral p-n and n+ -n-junctions and electrodes lying on the opposing sidewalls of the island. Excellent electrical performance was demonstrated, revealing a strong potential of ELO GaN with 3D device architecture for power switching applications. DOI: 10.1109/EDTM50988.2021.9420859 Web of Science Scopus Generalized Frequency Dependent Small Signal Model for High Frequency Analysis of AlGaN/GaN MOS-HEMTs Jadhav A., Ozawa T., Baratov A., Asubar J.T., Kuzuhara M., Wakejima A., Yamashita S., Deki M., Honda Y., Roy S., Amano H., Sarkar B. IEEE Journal of the Electron Devices Society 9 巻 頁: 570 - 581 2021年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:IEEE Journal of the Electron Devices Society Traditional lumped small signal equivalent circuit models of AlGaN/GaN metal oxide semiconductor high electron mobility transistors (MOS-HEMTs) are made up of constant valued circuit elements. Such models are unable to capture the high frequency behavior (above 20 GHz) of the device. In this work, a modified small signal equivalent circuit model of AlGaN/GaN MOS-HEMTs is presented. The key feature of the proposed model is that the values of the different circuit elements in the model are considered to be frequency dependent in nature and not constants. The frequency dependent value of each circuit element is mathematically represented using polynomial functions where the coefficients of the functions are determined via a least-square curve fitting approach. This frequency dependent attribute of the circuit element values ensures that the proposed model is very accurate at high frequencies without sacrificing the compactness of the model topology. The accuracy of the proposed model has been verified up to 50 GHz using experimentally measured Y-parameters of AlGaN/GaN MOS-HEMTs having a different gate dielectric and gate length. DOI: 10.1109/JEDS.2021.3081463 Web of Science Scopus Development of UV-C laser diodes on AlN substrate Kushimoto M. Proceedings of SPIE - The International Society for Optical Engineering 11686 巻 2021年 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Proceedings of SPIE - The International Society for Optical Engineering DOI: 10.1117/12.2575872 Scopus Decrease in the injection efficiency and generation of midgap states in UV-C LEDs: A model based on rate equations Piva F. Proceedings of SPIE - The International Society for Optical Engineering 11686 巻 2021年 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Proceedings of SPIE - The International Society for Optical Engineering DOI: 10.1117/12.2578134 Scopus Electrical properties of GaN metal-insulator-semiconductor field-effect transistors with Al2O3/GaN interfaces formed on vicinal Ga-polar and nonpolar surfaces Ando, Y; Nagamatsu, K; Deki, M; Taoka, N; Tanaka, A; Nitta, S; Honda, Y; Nakamura, T; Amano, H APPLIED PHYSICS LETTERS 117 巻 ( 24 ) 頁: 242104 2020年12月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1063/5.0028516 Web of Science The 2020 UV emitter roadmap Amano H., Collazo R., De Santi C., Einfeldt S., Funato M., Glaab J., Hagedorn S., Hirano A., Hirayama H., Ishii R., Kashima Y., Kawakami Y., Kirste R., Kneissl M., Martin R., Mehnke F., Meneghini M., Ougazzaden A., Parbrook P.J., Rajan S., Reddy P., Römer F., Ruschel J., Sarkar B., Scholz F., Schowalter L.J., Shields P., Sitar Z., Sulmoni L., Wang T., Wernicke T., Weyers M., Witzigmann B., Wu Y.R., Wunderer T., Zhang Y. Journal of Physics D: Applied Physics 53 巻 ( 50 ) 頁: 503001 2020年12月 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Journal of Physics D: Applied Physics Solid state UV emitters have many advantages over conventional UV sources. The (Al,In,Ga)N material system is best suited to produce LEDs and laser diodes from 400 nm down to 210 nm - due to its large and tuneable direct band gap, n- and p-doping capability up to the largest bandgap material AlN and a growth and fabrication technology compatible with the current visible InGaN-based LED production. However AlGaN based UV-emitters still suffer from numerous challenges compared to their visible counterparts that become most obvious by consideration of their light output power, operation voltage and long term stability. Most of these challenges are related to the large bandgap of the materials. However, the development since the first realization of UV electroluminescence in the 1970s shows that an improvement in understanding and technology allows the performance of UV emitters to be pushed far beyond the current state. One example is the very recent realization of edge emitting laser diodes emitting in the UVC at 271.8 nm and in the UVB spectral range at 298 nm. This roadmap summarizes the current state of the art for the most important aspects of UV emitters, their challenges and provides an outlook for future developments. DOI: 10.1088/1361-6463/aba64c Web of Science Scopus Detailed analysis of Ga-rich current pathways created in an n-AlThe microscopic structural and optical characteristics of AlGaN light-emitting diodes (LEDs) fabricated on the AlN templates with dense macrosteps are shown to clarify the origin of their high internal quantum efficiency of radiation (IQE). The cross-sectional transmission electron microscopy observations under the high-angle annular dark field scanning mode and microscopic energy dispersive X-ray spectroscopy revealed that the AlGaN cladding layer under the AlGaN quantum well (QW) layer had a microscopic compositional modulation, which originates from the macrosteps at the AlN template surface. Moreover, Ga-rich portions in the cladding layer behaved as current micropaths, and the micropaths are connected with the carrier localization structure formed in QWs. The in-plane cathodoluminescence (CL) spectroscopy showed a significant inhomogeneity of the CL characteristics. The gentle slopes at the sample surface showed brighter emissions with a lower peak photon energy, confirming the carrier localization. This carrier localization structure in the QWs combined with the current micropaths in the cladding layer can increase the IQE as well as external quantum efficiency of the AlGaN LEDs.
DOI: 10.19009/jjacg.47-3-04 CiNii Research Role of defects in the mid-term degradation of UV-B LEDs investigated by optical and DLTS measurements Piva F., De Santi C., Deki M., Kushimoto M., Amano H., Tomozawa H., Shibata N., Meneghesso G., Zanoni E., Meneghini M. GALLIUM NITRIDE MATERIALS AND DEVICES XV 11280 巻 頁: 1128015 2020年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Proceedings of SPIE - The International Society for Optical Engineering AlGaN-based UltraViolet Light Emitting Diodes (UV LEDs) are promising devices for replacing the conventional UV lamps, which contain toxic substances like mercury, in order to have smaller devices, lower operating voltage and the possibility of tuning the emission wavelength by changing the Al and Ga content in the alloy. However, UV-LEDs may suffer from a relatively fast degradation of electrical and optical characteristics, that can be due to the generation of defects that increase the Shockley-Read-Hall (SRH) recombination components. The aim of this paper is to study the behavior of UV-B LEDs submitted to a constant current stress, through electrical, optical and spectral characterization, and capacitance deep-level transient spectroscopy (C-DLTS). The results of this analysis demonstrate that UV-B LEDs show a decrease in the driving voltage, probably correlated with the increased activation of the Mg dopant, and an increase in subthreshold forward current, ascribed to the generation of mid-gap defects caused by the stress. We also found a strong optical degradation at low current levels, that indicates the increase in SRH recombination, probably due to the increased density of mid-gap defects. To investigate on the origin of the defects, we carried out C-DLTS measurements; the results indicate the presence of Mg-related defects and/or intrinsic defects related to the GaN growth. Moreover, after stress we notice the appearance of a peak that is strictly related to the increase of mid-gap defects generated during the stress. DOI: 10.1117/12.2544704 Web of Science Scopus Low leakage Mg-compensated GaN Schottky diodes on free-standing GaN substrate for high energy α-particle detection Sandupatia, A; Arulkurnaran, S; Ranjan, K; Ng, GI; Murumu, PP; Kennedy, J; Deki, M; Nitta, S; Honda, Y; Amano, H 2020 IEEE ELECTRON DEVICES TECHNOLOGY AND MANUFACTURING CONFERENCE (EDTM 2020) 2020年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Web of Science Dielectric Ruduced Surface Field Effect on Vertical GaN-on-GaN Nanowire Schottky Barrier Diodes Liao, YQ; Chen, T; Wang, J; Ando, Y; Yang, X; Watanabe, H; Hirotani, J; Kushimoto, M; Deki, M; Tanaka, A; Nitta, S; Honda, Y; Chen, KJ; Amano, H PROCEEDINGS OF THE 2020 32ND INTERNATIONAL SYMPOSIUM ON POWER SEMICONDUCTOR DEVICES AND ICS (ISPSD 2020) 2020-September 巻 頁: 349 - 352 2020年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Proceedings of the International Symposium on Power Semiconductor Devices and ICs In this work, gallium nitride (GaN) nanowire (NW) Schottky barrier diodes was fabricated using well-optimized top-down approach. As-fabricated $100 \times 800$-nm-diameter NWs SBD with high current density over 1kA/cm2 at a forward bias of 2.2V, a low differential specific ON-resistance of $0.15\mathrm{m} \Omega \cdot cm^{2}$ are demonstrated. By the virtue of dielectric Reduced Surface Field (RESURF) effect, the device also delivers a breakdown voltage of 515V, leading to a competitive Baliga&#39;s Figure of merit of 1.76 GW/cm2. DOI: 10.1109/ispsd46842.2020.9170101 Web of Science Scopus GaN基板向けレーザスライシング技術の開発 河口 大祐, 田中 敦之, 油井 俊樹, 伊ヶ崎 泰則, 和仁 陽太郎, 天野 浩 年次大会 2020 巻 ( 0 ) 頁: S16306 2020年 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:一般社団法人 日本機械学会 DOI: 10.1299/jsmemecj.2020.s16306 CiNii Research 高品質AlN 基板上UV-C レーザーダイオード 笹岡 千秋, 天野 浩 レーザー研究 48 巻 ( 8 ) 頁: 427 2020年 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:一般社団法人 レーザー学会 DOI: 10.2184/lsj.48.8_427 CiNii Research Improvement of The Light Output of Blue InGaN-Based Light Emitting Diodes by Using a Buried Stripe -Type n-Contact and Reflective Bonding Pad Kim, JH; Lee, YW; Im, HS; Oh, CH; Shim, JI; Kang, D; Seong, TY; Amano, H ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY 9 巻 ( 1 ) 頁: 015021 2019年12月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:ECS Journal of Solid State Science and Technology To enhance the light output of blue InGaN-based light emitting diodes (LEDs), a buried stripe-type n-electrode, expanded stripe-type p-electrode, and reflective p-bonding pad were employed. Flip-chip (FC) LEDs with the expanded p-electrode gave forward voltages of 2.99-3.11 V at 100 mA and series resistances of 3.28-3.94 Ω. The expanded p-electrode FCLED fabricated with 375 nm-thick window and TiO2 adhesion layers produced 22.7% higher light output at 21 A/cm2 than conventional FCLEDs. The expanded p-electrode FCLEDs revealed better current spreading efficiency than the c-FCLED, indicating the importance of the use of an optimised window and TiO2 adhesion layers. DOI: 10.1149/2.0462001JSS Web of Science Scopus Two-dimensional analysis of the nonuniform quantum yields of multiple quantum wells for AlGaN-based deep-ultraviolet LEDs grown on AlN templates with dense macrosteps using cathodoluminescence spectroscopy Nagasawa Y., Sugie R., Kojima K., Hirano A., Ippommatsu M., Honda Y., Amano H., Akasaki I., Chichibu S.F. Journal of Applied Physics 126 巻 ( 21 ) 頁: 215703 2019年12月 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Journal of Applied Physics AlGaN-based deep-ultraviolet light-emitting diodes (LEDs) incorporating uneven multiple quantum wells (MQWs) with inclined and terrace zones, which were fabricated on an AlN template with dense macrosteps, have exhibited a high internal quantum efficiency (IQE). To investigate the microscopic structure of uneven MQWs, cathodoluminescence (CL) mapping characterization was carried out, and the maps of the CL intensity at 300 K relative to that at 38 K were obtained for uneven MQWs that targeted 265 and 285 nm LEDs. At an electron beam current of less than 1.0 nA, the signals from inclined and terrace zones of the uneven MQWs were confirmed to satisfy the nonsaturated excitation condition at 300 K. Nonradiative recombination (NR) was insufficiently frozen even at 38 K, specifically on the terraces in the 265 nm MQW, suggesting high concentrations of NR centers due to point defects (PDs). In contrast, NR in the 285 nm MQW at 38 K was closer to freeze-out. The concentration of PDs in the 285 nm MQW was likely to be lower than that in the 265 nm MQW. Finally, the ratios of the CL intensity at 300 K to those at 38 K were mapped, demonstrating an approach to creating an approximate map of IQE. The values in the CL intensity ratio maps are discussed by considering the analytical error factors. The results support the model of localized current injection through Ga-rich stripe zones in the n-AlGaN cladding layer. DOI: 10.1063/1.5125623 Web of Science Scopus Suppression of Green Luminescence of Mg-Ion-Implanted GaN by Subsequent Implantation of Fluorine Ions at High Temperature Takahashi Masahiro, Tanaka Atsushi, Ando Yuto, Watanabe Hirotaka, Deki Manato, Kushimoto Maki, Nitta Shugo, Honda Yoshio, Shima Kohei, Kojima Kazunobu, Chichibu Shigefusa F., Chen Kevin J., Amano Hiroshi PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 257 巻 頁: 1900554 2019年12月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1002/pssb.201900554 Web of Science A 271.8 nm deep-ultraviolet laser diode for room temperature operation Zhang Ziyi, Kushimoto Maki, Sakai Tadayoshi, Sugiyama Naoharu, Schowalter Leo J., Sasaoka Chiaki, Amano Hiroshi APPLIED PHYSICS EXPRESS 12 巻 ( 12 ) 頁: 124003 2019年12月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.7567/1882-0786/ab50e0 Web of Science Untwinned semipolar (10(1)over-bar3) AlxGa1-xN layers grown on m-plane sapphire Dinh Duc V., Hu Nan, Amano Hiroshi, Honda Yoshio, Pristovsek Markus SEMICONDUCTOR SCIENCE AND TECHNOLOGY 34 巻 ( 12 ) 頁: 125012 2019年12月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1088/1361-6641/ab4d2c Web of Science Low Voltage High-Energy α-Particle Detectors by GaN-on-GaN Schottky Diodes with Record-High Charge Collection Efficiency Sandupatla, A; Arulkumaran, S; Ranjan, K; Ng, GI; Murmu, PP; Kennedy, J; Nitta, S; Honda, Y; Deki, M; Amano, H SENSORS 19 巻 ( 23 ) 頁: 5107 2019年12月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Sensors (Switzerland) A low voltage (–20 V) operating high-energy (5.48 MeV) α-particle detector with a high charge collection efficiency (CCE) of approximately 65% was observed from the compensated (7.7 × 1014 /cm3) metalorganic vapor phase epitaxy (MOVPE) grown 15 µm thick drift layer gallium nitride (GaN) Schottky diodes on free-standing n+-GaN substrate. The observed CCE was 30% higher than the bulk GaN (400 µm)-based Schottky barrier diodes (SBD) at –20 V. This is the first report of α–particle detection at 5.48 MeV with a high CCE at –20 V operation. In addition, the detectors also exhibited a three-times smaller variation in CCE (0.12 %/V) with a change in bias conditions from –120 V to –20 V. The dramatic reduction in CCE variation with voltage and improved CCE was a result of the reduced charge carrier density (CCD) due to the compensation by Mg in the grown drift layer (DL), which resulted in the increased depletion width (DW) of the fabricated GaN SBDs. The SBDs also reached a CCE of approximately 96.7% at –300 V. DOI: 10.3390/s19235107 Web of Science Scopus PubMed Improvement in the Reliability of AlGaInP-Based Light-Emitting Diode Package Using Optimal Silicone and Leadframe Structure Kim Ho-Young, Lee Jong Woo, Moon Young Min, Oh Jeong Tak, Jeong Hwan-Hee, Song June-O, Seong Tae-Yeon, Kneissl Michael, Amano Hiroshi ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY 9 巻 ( 1 ) 頁: 015014 2019年11月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1149/2.0332001JSS Web of Science Aluminium incorporation in polar, semi- and non-polar AlGaN layers: a comparative study of x-ray diffraction and optical properties Duc V Dinh, Hu Nan, Honda Yoshio, Amano Hiroshi, Pristovsek Markus SCIENTIFIC REPORTS 9 巻 頁: 15802 2019年11月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1038/s41598-019-52067-y Web of Science Hole injection mechanism in the quantum wells of blue light emitting diode with V pits for micro-display application Kang, D; Oh, JT; Song, JO; Seong, TY; Kneissl, M; Amano, H APPLIED PHYSICS EXPRESS 12 巻 ( 10 ) 頁: 102016 2019年10月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.7567/1882-0786/ab45d1 Web of Science V-shaped dislocations in a GaN epitaxial layer on GaN substrate Tanaka Atsushi, Nagamatsu Kentaro, Usami Shigeyoshi, Kushimoto Maki, Deki Manato, Nitta Shugo, Honda Yoshio, Bockowski Michal, Amano Hiroshi AIP ADVANCES 9 巻 ( 9 ) 頁: 095002 2019年9月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1063/1.5114866 Web of Science Stability and degradation of AlGaN-based UV-B LEDs: Role of doping and semiconductor defects Piva F., De Santi C., Deki M., Kushimoto M., Amano H., Tomozawa H., Shibata N., Meneghesso G., Zanoni E., Meneghini M. Microelectronics Reliability 100-101 巻 頁: 113418 2019年9月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Microelectronics Reliability Within this paper, we present an extensive analysis of the degradation of UV-B light-emitting diodes (LEDs) submitted to constant current stress. The study is based on combined electrical, optical and spectral characterization, and capacitance deep-level transient spectroscopy (C-DLTS). The results of this analysis demonstrate that the decrease in the optical power during the stress is stronger at low measuring current levels, indicating that the degradation is related to the increase in Shockley-Read-Hall (SRH) recombination. The electrical characterization shows a decrease in the driving voltage, probably due to an increased activation of the Mg dopant, and an increase in the sub-threshold forward current, that suggest a generation of mid-gap states during the stress. C-DLTS measurements were carried out to study the variation in defects concentration after stress; the most relevant traps were ascribed to the presence of Mg doping and/or to intrinsic defects related to the GaN growth. DOI: 10.1016/j.microrel.2019.113418 Web of Science Scopus Via-Hole-Type Flip-Chip Packaging to Improve the Thermal Characteristics and Reliability of Blue Light Emitting Diodes Kim, HY; Lim, CM; Kim, KS; Oh, JT; Jeong, HH; Song, JO; Seong, TY; Amano, H ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY 8 巻 ( 9 ) 頁: Q165 - Q170 2019年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:ECS Journal of Solid State Science and Technology We investigated the effect of via-holes in the lead-frame on the reliability of blue flip-chip light-emitting diodes (FCLEDs). For bonding, conventional Sn-Ag(3.0%)-Cu(0.5%) solder (SAC) and Ag sintered paste were adopted. Lateral LED, conventional FCLED (c-FCLED), and via-hole FCLED gave efficacies of 218.5, 221.6 and 225 lm/W at 30 mA. The lateral LED sample (bonding material: silicone), c-FCLED sample (SAC), via-hole-type sample (Ag sinter), and via-hole-type sample (SAC) exhibited total thermal resistance of 15.24, 10.19, 8.95, and 11.79 K/W, respectively. The humidity/temperature/H2S gas reliability examinations showed that unlike the via-hole-type samples, the lumen of the c-FCLED was fallen by 15.0% after exposure for 500 h. Furthermore, the c-FCLED exhibited a 19.6% higher forward voltage than the via-hole FCLED after 1,000 thermal-cycles. SEM results showed that unlike the via-hole type FCLED, the c-FCLED underwent cracking after thermal cycle of 1000 times. DOI: 10.1149/2.0171909jss Web of Science Scopus Combined effects of V pits and chip size on the electrical and optical properties of green InGaN-based light-emitting diodes Kim Dae-Hyun, Park Young Soo, Kang Daesung, Kim Kyoung-Kook, Seong Tae-Yeon, Amano Hiroshi JOURNAL OF ALLOYS AND COMPOUNDS 796 巻 頁: 146-152 2019年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1016/j.jallcom.2019.05.070 Web of Science Indium Incorporation into InGaN Quantum Wells Grown on GaN Narrow Stripes Sarzynski Marcin, Grzanka Ewa, Grzanka Szymon, Targowski Grzegorz, Czernecki Robert, Reszka Anna, Holy Vaclav, Nitta Shugo, Liu Zhibin, Amano Hiroshi, Leszczynski Mike MATERIALS 12 巻 ( 16 ) 頁: 2583 2019年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.3390/ma12162583 Web of Science Influence of Temperature-Dependent Substrate Decomposition on Graphene for Separable GaN Growth Park Jeong-Hwan, Lee Jun-Yeob, Park Mun-Do, Min Jung-Hong, Lee Je-Sung, Yang Xu, Kang Seokjin, Kim Sang-Jo, Jeong Woo-Lim, Amano Hiroshi, Lee Dong-Seon ADVANCED MATERIALS INTERFACES 6 巻 頁: 1900821 2019年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1002/admi.201900821 Web of Science Fabrication of a GaInN/GaInP/GaInAs/Ge four-junction solar cell using the wafer bonding technology Takahashi, K; Shinoda, R; Mitsufuji, S; Iwaya, M; Kamiyama, S; Takeuchi, T; Hattori, T; Akasaki, I; Amano, H JAPANESE JOURNAL OF APPLIED PHYSICS 58 巻 ( 7 ) 頁: 072003 2019年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Japanese Journal of Applied Physics We fabricated a GaInN/GaInP/GaInAs/Ge four-junction solar cell by wafer bonding a GaInN solar cell and a GaInP/GaInAs/Ge three-junction solar cell. We performed our wafer bonding at high pressure (500 N) and temperature (450 °C) by using p-type GaN and n-type GaAs. The open-circuit voltage (V OC), J SC, and fill factor of our four-junction solar cell under the condition of AM 1.5 G, i.e., 1 sun are 2.85 V, 0.219 mA cm-2, and 0.74, respectively. The improved V OC of our four-junction solar cells was confirmed by a series connection. The J SC is almost comparable to the theoretical value (itself based on the assumption of an ideal series junction), but the V OC is approximately 1 V less than that predicted by theory. Our research will improve the solar cell efficiency and help meet future energy needs. DOI: 10.7567/1347-4065/ab26ad Web of Science Scopus Origin of acceptor diffusion into silicon substrate during GaN growth by metal organic chemical vapor deposition Matsumoto, K; Ono, T; Honda, Y; Torigoe, K; Kushimoto, M; Amano, H JAPANESE JOURNAL OF APPLIED PHYSICS 58 巻 ( 7 ) 頁: 075502 2019年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Japanese Journal of Applied Physics This study investigated the change in carrier concentration near the surface of a silicon substrate during gallium nitride (GaN) growth with an aluminum nitride (AlN) buffer layer. It was observed that aluminum, gallium, and carbon diffused into the silicon substrate during the growth process and that the carrier concentration increased with increasing concentration of aluminum and gallium impurities. The gallium that diffused into the silicon substrate was identified as having originated from the gallium that decomposed on the reactor wall during the growth process and the gallium introduced onto the silicon substrate during GaN growth. In contrast, the amount of aluminum that diffused into the substrate was influenced by the duration of the trimethylaluminum (TMAl) flow: A long duration of the TMAl flow step before AlN growth led to a high aluminum concentration near the substrate surface. DOI: 10.7567/1347-4065/ab2657 Web of Science Scopus Ammonia decomposition and reaction by high-resolution mass spectrometry for group III - Nitride epitaxial growth Ye Zheng, Nitta Shugo, Nagamatsu Kentaro, Fujimoto Naoki, Kushimoto Maki, Deki Manato, Tanaka Atsushi, Honda Yoshio, Pristovsek Markus, Amano Hiroshi JOURNAL OF CRYSTAL GROWTH 516 巻 頁: 63-66 2019年6月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1016/j.jcrysgro.2019.03.025 Web of Science Direct evidence of Mg diffusion through threading mixed dislocations in GaN p-n diodes and its effect on reverse leakage current Usami Shigeyoshi, Mayama Norihito, Toda Kazuya, Tanaka Atsushi, Deki Manato, Nitta Shugo, Honda Yoshio, Amano Hiroshi APPLIED PHYSICS LETTERS 114 巻 ( 23 ) 頁: 232105 2019年6月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1063/1.5097767 Web of Science Computational fluid dynamics simulation study of the gas flow balance in a vertical HVPE reactor with a showerhead for low cost bulk GaN crystal growth Liu, Q; Fujimoto, N; Nitta, S; Honda, Y; Amano, H JAPANESE JOURNAL OF APPLIED PHYSICS 58 巻 ( SC ) 頁: SC1055 2019年6月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Japanese Journal of Applied Physics In order to make low cost bulk GaN single crystal with a high growth rate, we have built a vertical HVPE reactor with a showerhead configuration. The flow from the showerhead of the reactor is independently controlled by inner/outer two sets of gas supply lines. This special showerhead design makes the flow model different from the conventional showerhead reactors. We have employed a finite element-based simulator to study the fluid dynamic and crystal growth of this inner/outer flow independently controlled showerhead. Two simulation experiments were performed. One experiment has demonstrated that both growth rate and Ga yield can be improved without compromising the uniformity by controlling the different input parameters of inner and outer flow on the showerhead, as compared with the conventional showerhead. The other experiment has demonstrated that the showerhead can be further optimized by changing the inner/outer area ratio and input parameters. DOI: 10.7567/1347-4065/ab124e Web of Science Scopus Monolithic integration of tricolor micro-LEDs and color mixing investigation by analog and digital dimming Robin, Y; Hemeret, F; D&#39;Inca, G; Pristovsek, M; Trassoudaine, A; Amano, H JAPANESE JOURNAL OF APPLIED PHYSICS 58 巻 ( SC ) 頁: SCCC06 2019年6月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Japanese Journal of Applied Physics We report on the growth, processing and optical characterization of monolithically integrated tricolor micro-LEDs. The 100 × 100 μm2 active area of the devices is composed of independent subpixels emitting in the blue, green and yellow-orange range with color saturation of over 90% for all bands. The gamut of the device is recorded by both digital and analog dimming, i.e. by pulse width modulation or by varying the current density. Results indicate color mixing performed by both methods leads to a rotated or distorted gamut significantly different from the one predicted by the CIE color model. We explain our findings in terms of quantum-confined Stark effect screening and efficiency droop at high current density, which modify the expected hue and brightness of mixed colors. DOI: 10.7567/1347-4065/ab06ae Web of Science Scopus Effect of photoelectrochemical etching and post-metallization annealing on gate controllability of AlGaN/GaN high electron mobility transistors Uemura, K; Deki, M; Honda, Y; Amano, H; Sato, T JAPANESE JOURNAL OF APPLIED PHYSICS 58 巻 ( SC ) 頁: SCCD20 2019年6月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Japanese Journal of Applied Physics Recessed-gate AlGaN/GaN metal-insulator-semiconductor (MIS) high electron mobility transistors (HEMTs) were fabricated by utilizing a photoelectrochemical (PEC) etching and a post-metallization annealing (PMA) process. In order to demonstrate the device performance and reliability, both electrical and optical electroluminescence (EL) properties were evaluated. The capacitance-voltage (C-V) characteristic showed that the PEC etching and subsequent PMA process enhanced the gate control of two-dimensional electron gas density. The PEC-etched-gate AlGaN/GaN MIS-HEMT showed the smallest sub-threshold slope of all the samples including planar-gate and inductively coupled plasma-etched-gate devices. Furthermore, the PEC-etched devices showed an extremely low 10-11 A mm-1 gate leakage current with no spot-like EL. These results indicated that the PEC etching and subsequent PMA process improved the electrical properties of the Al2O3/AlGaN interface, resulting in enhanced device performance of the AlGaN/GaN MIS-HEMTs. DOI: 10.7567/1347-4065/ab06b9 Web of Science Scopus Deeply and vertically etched butte structure of vertical GaN p-n diode with avalanche capability Fukushima, H; Usami, S; Ogura, M; Ando, Y; Tanaka, A; Deki, M; Kushimoto, M; Nitta, S; Honda, Y; Amano, H JAPANESE JOURNAL OF APPLIED PHYSICS 58 巻 ( SC ) 頁: SCCD25 2019年6月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Japanese Journal of Applied Physics A vertical p-n diode with a simple edge termination structure on a GaN free-standing substrate is demonstrated. The edge of this device is terminated simply by etching a drift layer deeply and vertically. A device simulation revealed that the electric field at the device edge was more relaxed and uniformly applied by etching the mesa deeper than the depletion region. The fabricated device showed low leakage current and avalanche capability, and its breakdown characteristics could be reproduced many times. By emission microscopy observation, we found that there was no leakage current at the side wall of the device and that avalanche breakdown occurred throughout the inside of the device. This indicates that the electric field crowding at the side wall of the device was completely suppressed and a uniform electric field distribution was obtained by this structure. DOI: 10.7567/1347-4065/ab106c Web of Science Scopus Correlation between nanopipes formed from screw dislocations during homoepitaxial growth by metal-organic vapor-phase epitaxy and reverse leakage current in vertical p-n diodes on a free-standing GaN substrates Usami, S; Tanaka, A; Fukushima, H; Ando, Y; Deki, M; Nitta, S; Honda, Y; Amano, H JAPANESE JOURNAL OF APPLIED PHYSICS 58 巻 ( SC ) 頁: SCCB24 2019年6月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Japanese Journal of Applied Physics We fabricated p-n diodes under different growth pressures on free-standing GaN substrates of the same quality and observed a noteworthy difference in the reverse leakage current. A large reverse leakage current was generated by nanopipes, which were formed from screw dislocations in the homoepitaxial layer. There were two types of screw dislocation observed in this study. The first type already existed in the substrate and the other was newly generated in the epilayer by the coalescence of edge and mixed dislocations. An increase in the growth pressure suppressed the transformation of screw dislocations into nanopipes, which led to a reduction in the reverse leakage current. To reduce the leakage current further, it is necessary to apply growth conditions that do not transform screw dislocation into nanopipes and to use a free-standing substrate without threading dislocations, that become nanopipes. DOI: 10.7567/1347-4065/ab1250 Web of Science Scopus Controlling the orientations of directional sputtered non- and semi-polar GaN/AlN layers Nan, H; Dinh, DV; Pristovsek, M; Honda, Y; Amano, H JAPANESE JOURNAL OF APPLIED PHYSICS 58 巻 ( SC ) 頁: SC1044 2019年6月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Japanese Journal of Applied Physics We have studied the impact on the surface orientation of different sputtered Al layers followed by AlN layers sputtered on m-plane sapphire. These initial layers were then overgrown by AlN and followed by GaN using metal-organic vapor phase epitaxy (MOVPE). By increasing sputtering time of the initial Al layer from 0 s to 15 s, we obtained single phase (10-10), (10-13) and (10-14) GaN/AlN layers. The thickness of the initial Al layer was estimated by optical transmission measurements to be about 0.5-1 nm for the (10-13) orientation, and >1 nm for the (10-14) orientation. After MOVPE growth, no trace of metallic Al was found by transmission electron microscopy, indicating that this layer was fully converted to AlN. DOI: 10.7567/1347-4065/ab1252 Web of Science Scopus Comparison of AlxGa1-xN multiple quantum wells designed for 265 and 285nm deep-ultraviolet LEDs grown on AlN templates having macrosteps Nagasawa Yosuke, Kojima Kazunobu, Hirano Akira, Ipponmatsu Masamichi, Honda Yoshio, Amano Hiroshi, Akasaki Isamu, Chichibu Shigefusa F. APPLIED PHYSICS EXPRESS 12 巻 ( 6 ) 頁: 064009 2019年6月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.7567/1882-0786/ab21a9 Web of Science Narrow Excitonic Lines in Core-Shell Nanorods With InGaN/GaN Quantum Wells Intersected by Basal Stacking Faults Evropeitsev Evgeniy A., Robin Yoann, Shubina Tatiana V., Bae Si-Young, Nitta Shugo, Kirilenko Demid A., Davydov Valery Y., Smirnov Alexandr N., Toropov Alexey A., Kushimoto Maki, Ivanov Sergey V., Amano Hiroshi PHYSICA STATUS SOLIDI B-BASIC SOLID STATE PHYSICS 256 巻 ( 6 ) 頁: 1800648 2019年6月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1002/pssb.201800648 Web of Science Morphological study of InGaN on GaN substrate by supersaturation (vol 508, pg 58, 2019) Liu Zhibin, Nitta Shugo, Robin Yoann, Kushimoto Maki, Deki Manato, Honda Yoshio, Pristovsek Markus, Sitar Zlatko, Amano Hiroshi JOURNAL OF CRYSTAL GROWTH 514 巻 頁: 13-13 2019年5月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1016/j.jcrysgro.2019.02.058 Web of Science Effect of substrate misorientation on the concentration of impurities and surface morphology of an epitaxial GaN layer on N-polar GaN substrate by MOVPE Nagamatsu Kentaro, Ando Yuto, Kono Tsukasa, Cheong Heajeong, Nitta Shugo, Honda Yoshio, Pristovsek Markus, Amano Hiroshi JOURNAL OF CRYSTAL GROWTH 512 巻 頁: 78-83 2019年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1016/j.jcrysgro.2019.02.013 Web of Science Nonpolar m-plane AlxGa1-xN layers grown on m-plane sapphire by MOVPE Duc V Dinh, Amano Hiroshi, Pristovsek Markus JOURNAL OF CRYSTAL GROWTH 512 巻 頁: 100-104 2019年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1016/j.jcrysgro.2019.02.020 Web of Science The emergence and prospects of deep-ultraviolet light-emitting diode technologies Kneissl Michael, Seong Tae-Yeon, Han Jung, Amano Hiroshi NATURE PHOTONICS 13 巻 ( 4 ) 頁: 233-244 2019年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1038/s41566-019-0359-9 Web of Science GaN drift-layer thickness effects in vertical Schottky barrier diodes on free-standing HVPE GaN substrates Sandupatla A., Arulkumaran S., Ng G. I., Ranjan K., Deki M., Nitta S., Honda Y., Amano H. AIP ADVANCES 9 巻 ( 4 ) 頁: 045007 2019年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1063/1.5087491 Web of Science Transfer-free fabrication of a graphene transparent electrode on a GaN-based light-emitting diode using the direct precipitation method Yamada, J; Usami, S; Ueda, Y; Honda, Y; Amano, H; Maruyama, T; Naritsuka, S JAPANESE JOURNAL OF APPLIED PHYSICS 58 巻 ( 4 ) 頁: 040904 2019年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Japanese Journal of Applied Physics In order to advance the mass production of graphene devices, it is beneficial to avoid the difficulty graphene transfer process. Direct precipitation of graphene using a tungsten capping layer is convenient for this purpose, and is quite simple and compatible with conventional semiconductor fabrication processes. In this study, multilayer graphene was directly precipitated on a wafer of GaN-based blue LEDs to form a transparent electrode. The fabricated LED exhibited superior I-V characteristics and emitted blue luminescence around the probe of the electrode. DOI: 10.7567/1347-4065/aafe70 Web of Science Scopus Effect of gas phase temperature on InGaN grown by metalorganic vapor phase epitaxy Liu Zhibin, Nitta Shugo, Usami Shigeyoshi, Robin Yoann, Kushimoto Maki, Deki Manato, Honda Yoshio, Pristovsek Markus, Amano Hiroshi JOURNAL OF CRYSTAL GROWTH 509 巻 頁: 50-53 2019年3月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1016/j.jcrysgro.2018.12.007 Web of Science GaN-on-Si resonant-cavity light-emitting diode incorporating top and bottom dielectric distributed Bragg reflectors Cai Wei, Yuan Jialei, Ni Shuyu, Shi Zheng, Zhou Weidong, Liu Yuhuai, Wang Yongjin, Amano Hiroshi APPLIED PHYSICS EXPRESS 12 巻 ( 3 ) 頁: 032004 2019年3月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.7567/1882-0786/ab023c Web of Science Fully Ion Implanted Normally-Off GaN DMOSFETs with ALD-Al2O3 Gate Dielectrics Yoshino Michitaka, Ando Yuto, Deki Manato, Toyabe Toru, Kuriyama Kazuo, Honda Yoshio, Nishimura Tomoaki, Amano Hiroshi, Kachi Tetsu, Nakamura Tohru MATERIALS 12 巻 ( 5 ) 頁: 689 2019年3月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.3390/ma12050689 Web of Science Effects of Drift Layer Thicknesses in Reverse Conduction Mechanism on Vertical GaN-on-GaN SBDs grown by MOCVD Abhinay S., Arulkumaran S., Ng G.I., Ranjan K., Deki M., Nitta S., Honda Y., Amano H. 2019 Electron Devices Technology and Manufacturing Conference, EDTM 2019 頁: 106 - 108 2019年3月 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:2019 Electron Devices Technology and Manufacturing Conference, EDTM 2019 Effect of drift layer thicknesses (DLT) (2, 15 and 30 μm) in reverse current conduction mechanisms of vertical GaN-on-GaN Schottky Barrier Diodes grown MOCVD has been investigated for the first time. The conduction mechanism is changing from thermionic field emission (TFE) to thermionic emission (TE) when the DLT of GaN increases. The SBDs with DLT of 2 μm and 30 μm exhibit TFE through Poole-Frenkel emission and TE, respectively. However, the SBDs with DLT of 15 μm exhibit both TFE and TE. Activation energy (Ea) of traps was also calculated to be 0.69 eV for 2 μm, 0.38 for 15 μm and 0.4 eV for 30 μm respectively. Ea of 0.69 eV and 0.4 eV could be associated with screw threading dislocations and the presence of Mg in the grown drift layer, respectively. DOI: 10.1109/EDTM.2019.8731215 Scopus GaN薄膜における貫通転位およびナノパイプm壁面の第一原理計算に基づく電子状態解析 中野 崇志, 長川 健太, 洗平 昌晃, 白石 賢二, 押山 淳, 宇佐美 茂佳, 草場 彰, 寒川 義裕, 田中 敦之, 本田 善央, 天野 浩 応用物理学会学術講演会講演予稿集 2019.1 巻 ( 0 ) 頁: 3122 - 3122 2019年2月 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:公益社団法人 応用物理学会 DOI: 10.11470/jsapmeeting.2019.1.0_3122 CiNii Research Morphological study of InGaN on GaN substrate by supersaturation Liu Zhibin, Nitta Shugo, Robin Yoann, Kushimoto Maki, Deki Manato, Honda Yoshio, Pristovsek Markus, Amano Hiroshi JOURNAL OF CRYSTAL GROWTH 508 巻 頁: 58-65 2019年2月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1016/j.jcrysgro.2018.12.028 Web of Science How to obtain metal-polar untwinned high-quality (10-13) GaN on m-plane sapphire Hu, N; Dinh, DV; Pristovsek, M; Honda, Y; Amano, H JOURNAL OF CRYSTAL GROWTH 507 巻 頁: 205 - 208 2019年2月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Journal of Crystal Growth Directional sputtering of Al and AlN on (1 0 −1 0) sapphire was used to obtain metal-polar (1 0 −1 3) templates. After overgrowth with AlN and GaN using metal-organic vapor phase epitaxy, we obtained untwinned (1 0 −1 3) GaN layers. Full width at half maximum of the X-ray rocking curve of symmetric (1 0 −1 3) GaN is less than 550 arcsec along both [3 0 −3 −2]GaN and [1 −2 1 0]GaN directions. Ga-polarity of the layers was confirmed by high-resolution scanning transmission electron microscopy. Careful optimization of time and temperature of the initial Al sputtered layer was a key parameter to achieve high quality GaN templates. DOI: 10.1016/j.jcrysgro.2018.11.013 Web of Science Scopus 高感度電子線ホログラフィーによるGaN系半導体のドーパント濃度分布の観察 仲野 靖孝, 松本 実子, 穴田 智史, 山本 和生, 石川 由加里, 平山 司, 安藤 悠人, 小倉 昌也, 田中 敦之, 本田 善央, 天野 浩 まてりあ 58 巻 ( 2 ) 頁: 103 - 103 2019年2月 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:公益社団法人 日本金属学会 DOI: 10.2320/materia.58.103 CiNii Research Pole figure analysis from electron backscatter diffraction-an effective method of evaluating fiber-textured silicon thin films as seed layers for epitaxy Hainey, M; Robin, Y; Amano, H; Usami, N APPLIED PHYSICS EXPRESS 12 巻 ( 2 ) 2019年2月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Applied Physics Express Because of their >95% (111) surface orientation and very large (10-300 μm) grain sizes, sub-50 nm Group IV thin films fabricated by metal-induced crystallization are promising seed layers for epitaxy. However, methods for evaluating Group IV film quality for subsequent homo-and heteroepitaxial growth have not been widely reported. Here, we show how pole figures obtained by electron backscatter diffraction allow for texture analysis and measurement of grain misorientation. Correlations with Group IV thin film processing parameters such as annealing temperature and film quality in heteroepitaxially grown GaN films are developed. DOI: 10.7567/1882-0786/aafb26 Web of Science Scopus Vertical GaN p-n diode with deeply etched mesa and the capability of avalanche breakdown Fukushima, H; Usami, S; Ogura, M; Ando, Y; Tanaka, A; Deki, M; Kushimoto, M; Nitta, S; Honda, Y; Amano, H APPLIED PHYSICS EXPRESS 12 巻 ( 2 ) 頁: 026502 2019年2月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Applied Physics Express A simple structure with high breakdown voltage and a low leakage current of a vertical GaN p-n diode on a GaN free-standing substrate is demonstrated. We describe a vertical p-n diode with a simple edge termination that has a drift layer etched deeply and vertically. A device simulation revealed that the electric field was more relaxed at the device edge and applied uniformly in the entire device with increasing etching depth. We fabricated the simulated structure and succeeded in reducing the leakage current and improving the breakdown voltage. With this structure, a stable avalanche breakdown can be observed. DOI: 10.7567/1882-0786/aafdb9 Web of Science Scopus Compositional control of homogeneous InGaN nanowires with the In content up to 90. Zeghouane M, Avit G, André Y, Bougerol C, Robin Y, Ferret P, Castelluci D, Gil E, Dubrovskii VG, Amano H, Trassoudaine A Nanotechnology 30 巻 ( 4 ) 頁: 044001 2019年1月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Nanotechnology Homogenous InGaN nanowires with a controlled indium composition up to 90% are grown on GaN/c-Al2O3 templates by catalyst-free hydride vapor phase epitaxy using InCl3 and GaCl as group III element precursors. The influence of the partial pressures on the growth rate and composition of InGaN nanowires is investigated. It is shown how the InN mole fraction in nanowires can be finely tuned by changing the vapor phase composition. Thermodynamic calculations are presented that take into account different interconnected reactions in the vapor phase and show a good agreement with the compositional data. Energy dispersive x-ray spectroscopy profiles performed on single nanowires show a homogenous indium composition along the entire nanowire length. X-ray diffraction measurements performed on nanowires arrays confirm these data. High-resolution transmission electron microscopy analysis shows the wurtzite crystal structure with a reduced defect density for InGaN nanowires with the highest indium content. DOI: 10.1088/1361-6528/aaec39 Web of Science Scopus PubMed Localization and transient emission properties in InGaN/GaN quantum wells of different polarities within core- shell nanorods Robin, Y; Evropeitsev, EA; Shubina, TV; Kirilenko, DA; Davydov, VY; Smirnov, AN; Toropov, AA; Eliseyev, IA; Bae, SY; Kushimoto, M; Nitta, S; Ivanov, SV; Amano, H NANOSCALE 11 巻 ( 1 ) 頁: 193 - 199 2019年1月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Nanoscale Transient photoluminescence (PL) characteristics and localization phenomena in InGaN/GaN core-shell nanorods (NRs) were investigated from 6 K up to 285 K. The NRs exhibit three well-defined PL bands in the near-UV, blue, and green range ascribed to the emission of quantum well (QW) areas situated at the (1.00) sidewalls, (10.1) top facets, and (00.1) tip, respectively. At low temperature, time-resolved PL shows a fast decay time of about 0.5 ns for the semi- and non-polar QWs, while the polar QWs exhibit at least a twice-longer time. Rapid delocalization of carriers above 50 K indicates shallow potential fluctuations in the QWs. At room temperature, the characteristic fast PL decay time of the three QW bands stabilizes around 300 ps. The slow decaying PL components have different characteristic decay times that are explained by additional localization at basal stacking faults (BSFs), taking into account the quantum confined Stark effect. In addition, narrow excitonic luminescence lines are observed in the BSF-enriched polar QWs, providing direct evidence of the impact of the BSF/QW crossings on the optical properties of the NRs. A PL rise time of about 100 ps does not show any deviation between bands. These findings are suggestive of similar transport mechanisms in temperature equilibrium without inter-facet transport between different QWs. We believe that predictable transient characteristics can play a key role in creating uniform NR ensembles for device applications. DOI: 10.1039/c8nr05863f Web of Science Scopus PubMed Carrier localization structure combined with current micropaths in AlGaN quantum wells grown on an AlN template with macrosteps Kojima K., Nagasawa Y., Hirano A., Ippommatsu M., Honda Y., Amano H., Akasaki I., Chichibu S.F. Applied Physics Letters 114 巻 ( 1 ) 頁: 011102 2019年1月 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Applied Physics Letters The microscopic structural and optical characteristics of AlGaN-based light-emitting diodes grown on AlN templates with macrosteps were evaluated. Cross-sectional transmission electron microscopy in the high-angle annular dark field scanning mode and microscopic energy dispersive X-ray spectroscopy reveal that the AlGaN cladding layer under the AlGaN quantum wells (QWs) has microscopic compositional modulations originating from the macrosteps at the AlN template surface. The Ga-rich oblique zones in the cladding layer likely behave as current micropaths. These micropaths are connected to the carrier localization structure, which is formed by the modulation of both the well widths and the compositions of the QWs. In-plane spatially-resolved cathodoluminescence (CL) spectroscopy indicated significant inhomogeneity of the CL characteristics: the brighter emission with a lower peak photon energy confirms the existence of the carrier localization structure in the QWs. Carrier localization in the QWs along with the current micropaths in the AlGaN cladding layer appears to increase the external quantum efficiency of AlGaN LEDs. DOI: 10.1063/1.5063735 Web of Science Scopus 286 nm monolithic multicomponent system Yuan, JL; Jiang, Y; Shi, Z; Gao, XM; Wang, YJ; Sun, XJ; Li, DB; Liu, YH; Amano, H JAPANESE JOURNAL OF APPLIED PHYSICS 58 巻 ( 1 ) 頁: 010909 2019年1月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Japanese Journal of Applied Physics We present a 286 nm monolithic multicomponent system in which two identical multiple quantum well (MQW) diodes merge with a waveguide together on a single chip. The monolithic multicomponent system allows all existing standard fabrication processes and establishes an optical link between two MQW-diodes because of the simultaneous emission-detection phenomenon. One MQW-diode transcribes electronic information into an optical signal to be coupled into a waveguide. The guided light then propagates along the waveguide to the other MQW-diode that converts the optical signal into an electronic one. A spatial light transmission at 50 Mbps is demonstrated using non-return-to-zero on-off keying modulation. DOI: 10.7567/1347-4065/aaf3aa Web of Science Scopus Electronic structure analysis of core structures of threading dislocations in GaN Nakano, T; Chokawa, K; Araidai, M; Shiraishi, K; Oshiyama, A; Kusaba, A; Kangawa, Y; Tanaka, A; Honda, Y; Amano, H 2019 COMPOUND SEMICONDUCTOR WEEK (CSW) 頁: . 2019年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:2019 Compound Semiconductor Week, CSW 2019 - Proceedings It is known that threading dislocations degrade the performance of GaN-based electronic devices. Electronic structure of threading dislocations in GaN is not fully understood. Accordingly, we examine the electronic structures of threading dislocations in GaN using first principles calculations based on density functional theory (DFT) and to clarify the origin of the leakage current. We have comprehensively studied the relation between threading core structures and electronic property in GaN thin films. Our calculation models of threading dislocations are the edge dislocations with Burgers vectors of 1/3 [11-20] and the screw dislocations with Burgers vectors of [0001]. We examined various core types of the threading dislocations. We found that both edge dislocations and screw dislocations do not cause the leakage currents in n-type GaN based devices because no defect level appears near the conduction band bottom. DOI: 10.1109/iciprm.2019.8819270 Web of Science Scopus Light-Emitting Diodes Materials, Processes, Devices and Applications Foreword Amano, H LIGHT-EMITTING DIODES: MATERIALS, PROCESSES, DEVICES AND APPLICATIONS 4 巻 頁: V - V 2019年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Web of Science MOVPE growth and high-temperature annealing of (10(1)over-bar0) AlN layers on (10(1)over-bar0) sapphire Dinh Duc V., Amano Hiroshi, Pristovsek Markus JOURNAL OF CRYSTAL GROWTH 502 巻 頁: 14-18 2018年11月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1016/j.jcrysgro.2018.09.001 Web of Science What is red? On the chromaticity of orange-red InGaN/GaN based LEDs Robin, Y; Pristovsek, M; Amano, H; Oehler, F; Oliver, RA; Humphreys, CJ JOURNAL OF APPLIED PHYSICS 124 巻 ( 18 ) 頁: 183102 2018年11月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Journal of Applied Physics The full width at half maximum (FWHM) of the luminescence of visible InGaN quantum well (QW) based emitters increases with wavelength. This broadening of the luminescence decreases the color saturation from 100% to about 70% up a wavelength shorter than 515 nm. For emission wavelengths longer than 515 nm, the saturation surprisingly increases again and reaches 95% beyond 560 nm. More important, in the yellow-red range, the perceived hue is strongly blue-shifted by a broad emission. This phenomenon is known as Abney effect, and it originates from the spectral sensitivities of the cone cells of the human eyes. As a consequence, for red InGaN QW based LEDs, the peak wavelength must be even further in the red. Based on a large set of QWs grown on different crystal orientations, we correlated the wavelength and the luminescence FWHM of InGaN/GaN QWs to build a model which predicts the perceived chromaticity, i.e., the apparent hue and saturation of yellow-red nitride LEDs. We also applied this model to (11-22), a-plane, and m-plane QWs and compared our data to the state-of-the-art of the literature. We concluded that the FWHM of the luminescence is a critical parameter to design and a further challenge for red InGaN-based light-emitting diodes. DOI: 10.1063/1.5047240 Web of Science Scopus Simultaneous Growth of Various InGaN/GaN Core-Shell Microstructures for Color Tunable Device Applications Robin, Y; Liao, YQ; Pristovsek, M; Amano, H PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE 215 巻 ( 21 ) 頁: 1800361 2018年11月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Physica Status Solidi (A) Applications and Materials Science An approach to simultaneously grow independent core-shell structures emitting at different wavelengths by selective area epitaxy is presented. By using seeds of different sizes, the monolithic integration of various GaN crystals including elongated nano-rods (NRs), micro-platelets (MPs), and a range of pyramid-like structures are demonstrated. Dominant non-polar sidewalls cover more than 75% of the surface area of the NRs, while the polar top facet are about 80% of the total surface of the MPs. InGaN/GaN quantum wells (QWs) deposited on these structures exhibit independent and well-separated emissions in the green–blue and orange–red ranges, respectively. The pyramid-like structures at intermediate seed sizes are more complex with semi-polar facets nearly totaling 60% of the total surface area, resulting in yellow luminescence strongly broadened by the nearby facets contributions. These results suggest the total surface area of each facets and the resulting optical properties of the crystals can be tailored by adjusting the size of the seeds. However, further improvements are required to locally enhance the vertical, pyramidal, and lateral growth of the GaN cores and increase the spectral purity of the different QWs. The approach presented is of interest to design multi-wavelength devices which requires independent subpixels of high color purity. DOI: 10.1002/pssa.201800361 Web of Science Scopus Analysis of negative electron affinity InGaN photocathode by temperature-programed desorption method Kashima, M; Sato, D; Koizumi, A; Nishitani, T; Honda, Y; Amano, H; Iijima, H; Meguro, T JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B 36 巻 ( 6 ) 頁: 06JK02 2018年11月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics A III-V semiconductor with a few monolayers of alkali metals (e.g., Cs) forms a negative electron affinity (NEA) surface, for which the vacuum level lies below the conduction band minimum of the base semiconductor. The photocathodes that form an NEA surface (NEA photocathodes) have various advantages, such as low emittance, a large current, high spin polarization, and ultrashort pulsed operation. The NEA-InGaN photocathode, which is sensitive to blue light, has been studied as a material for the next-generation robust photocathode. However, the proper conditions for forming NEA surfaces remain unknown. The authors consider whether the suitable process for NEA surfaces can be understood by investigating the relationship between the electron emission and the adsorption state of alkali metals. In this study, the relationship between the electron emission and the adsorption state of Cs on the p-type InGaN (0001) was analyzed by the temperature-programed desorption (TPD) method using a quadrupole mass spectrometer. From the results of the TPD measurements, it was shown that there were several adsorption states of Cs on InGaN. The quantum efficiency (QE), which indicates the ratio of emitted electrons to incident photons, increased while Cs desorption occurred. The authors divided the formation process of an NEA surface into several sections to investigate the adsorption states of Cs related to the electron emission and to discuss the reasons why the QE increased despite the desorbed Cs. From the results of the NEA activation in each section, it was shown that there were sections where the QE increased by reacting with O2 after Cs supply stopped. There is a possibility that several layers reacting with O2 and those not reacting with O2 are formed by performing NEA activation until the QE saturates. From the results of the TPD measurements in each section, it was suggested that there was a Cs peak at above 700 °C when the TPD method was carried out immediately after confirming the electron emission. Therefore, the adsorption state of Cs that formed a peak at above 700 °C had a close relation to the electron emission. It is considered that the increase of the QE in the TPD was affected by adsorbed Cs compounds that reacted with O2. Although the mechanism is not understood, it is known that the QE was increased by the reaction of Cs adsorbed compounds and O2 in previous studies. It was suspected that layers that reacted with O2 appeared from TPD and then the QE increased by reacting with O2. DOI: 10.1116/1.5048061 Web of Science Scopus Full-duplex light communication with a monolithic multicomponent system Wang Yongjin, Wang Xin, Zhu Bingcheng, Shi Zheng, Yuan Jialei, Gao Xumin, Liu Yuhuai, Sun Xiaojuan, Li Dabing, Amano Hiroshi LIGHT-SCIENCE & APPLICATIONS 7 巻 頁: 83 2018年10月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1038/s41377-018-0083-0 Web of Science Crystal engineering by tuning the growth kinetics of GaN 3-D microstructures in SAG-HVPE Avit Geoffrey, Zeghouane Mohammed, Andre Yamina, Castelluci Dominique, Gil Evelyne, Bae Si-Young, Amano Hiroshi, Trassoudaine Agnes CRYSTENGCOMM 20 巻 ( 40 ) 頁: 6207 - 6213 2018年10月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:CrystEngComm The growth of GaN 3-D microstructures is investigated by SAG-HVPE. Capitalizing on the properties of this kinetically-controlled process, the main experimental parameters and physical mechanisms that control the shaping of 3D GaN prisms and pyramids in SAG-HVPE are highlighted. Growth experiments performed on N-polar AlN/Si(100) and Ga-polar GaN/Si(111) substrates also provide insight into how to switch from a pyramid to a prismatic shape for a given substrate polarity. The aspect ratio of GaN rods could be tuned by playing with the HCl partial pressure additionally introduced during growth. The influence of both mass transport and surface kinetics is discussed, as the crystal growth rate varies with increasing surface area as time goes by. Ammonia treatment prior to the growth, aimed at blocking the r planes thanks to H2 passivation, is proposed to tune the morphology of the GaN rods. Raman spectroscopy performed on individual GaN rods shows no relevant strain field and no structural differences between the rods and state-of-the-art bulk GaN. DOI: 10.1039/c8ce01177j Web of Science Scopus researchmap Comparing high-purity c- and m-plane GaN layers for Schottky barrier diodes grown homoepitaxially by metalorganic vapor phase epitaxy Nagamatsu Kentaro, Ando Yuto, Ye Zheng, Barry Ousmane, Tanaka Atsushi, Deki Manato, Nitta Shugo, Honda Yoshio, Pristovsek Markus, Amano Hiroshi JAPANESE JOURNAL OF APPLIED PHYSICS 57 巻 ( 10 ) 頁: 105501 2018年10月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.7567/JJAP.57.105501 Web of Science High-temperature thermal annealing of nonpolar (10(1)over-bar0) AlN layers sputtered on (1 0(1)over-bar0) sapphire Dinh Duc V, Hu Nan, Honda Yoshio, Amano Hiroshi, Pristovsek Markus JOURNAL OF CRYSTAL GROWTH 498 巻 頁: 377-380 2018年9月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1016/j.jcrysgro.2018.07.015 Web of Science 「材料研究の楽しさ」 天野 浩 表面と真空 61 巻 ( 9 ) 頁: 565 - 567 2018年9月 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:公益社団法人 日本表面真空学会 半導体の王者は言わずと知れたSiである。市場規模を比べると,化合物半導体全部含めてもSiの1/10にも満たない。それでも化合物半導体,とりわけGaN系窒化物半導体にこだわっている理由は,この材料の物性自体がとても興味深いこと,およびSiでは出来ないことが出来る,或いは今後できそうだからである。本寄稿では,筆者が学生の頃からこれまで30年以上もの間取り組んでいるGaN系窒化物半導体材料の研究で,特に表面と真空について学んだことを中心に書かせて頂くことにする。 DOI: 10.1380/vss.61.565 CiNii Research Detailed study of effects of duration of pre-AIN-growth trimethylaluminum step on morphologies of GaN layers grown on silicon substrate by metal organic chemical vapor deposition Matsumoto Koji, Ono Toshiaki, Honda Yoshio, Murakami Satoshi, Kushimoto Maki, Amano Hiroshi JAPANESE JOURNAL OF APPLIED PHYSICS 57 巻 ( 9 ) 頁: 091001 2018年9月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.7567/JJAP.57.091001 Web of Science Reduction of Residual Impurities in Homoepitaxial m-Plane (10(1)over-bar0) GaN by Using N-2 Carrier Gas in Metalorganic Vapor Phase Epitaxy Barry Ousmane I., Lekhal Kaddour, Bae Si-Young, Lee Ho-Jun, Pristovsek Markus, Honda Yoshio, Amano Hiroshi PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS 12 巻 ( 8 ) 頁: 1800124 2018年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Physica Status Solidi - Rapid Research Letters The reduction of unintentional impurities in m-plane (1010) GaN homoepitaxial layers is demonstrated by using nitrogen (N2), as opposed to hydrogen (H2), as carrier gas in metalorganic vapor phase epitaxy (MOVPE). Secondary ion mass spectrometry (SIMS) analysis shows that the impurity levels of residual oxygen (O), carbon (C), and silicon (Si) are decreased by nearly one order of magnitude in N2-grown samples. Although the full width at half maximum (FWHM) values for the on-axis m-plane X-ray rocking curves of all specimens are quite similar (around 50 arcsec), plan-view scanning transmission electron microscopy (STEM) measurements reveal a clear reduction of dislocation densities in N2-grown films. Their origin is likely related to an initial surface roughening with H2 carrier gas, which also causes surface faceting resulting in the formation of large four-sided pyramidal hillocks, while using N2 results in smoother surfaces. Hence, MOVPE growth with N2 carrier gas is an effective method to lower the impurity incorporation in m-plane GaN materials in addition to reducing the formation of defects and improving the surface morphology, which can enable the development of high-performance GaN-based devices on non-polar surfaces. DOI: 10.1002/pssr.201800124 Web of Science Scopus researchmap Improvement of breakdown voltage of vertical GaN p-n junction diode with Ga2O3 passivated by sputtering Ueoka, Y; Deki, M; Honda, Y; Amano, H JAPANESE JOURNAL OF APPLIED PHYSICS 57 巻 ( 7 ) 頁: 070302 2018年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Japanese Journal of Applied Physics This article describes a new passivation process of Ga2O3, which consists by sputtering, for a vertical GaN p-n junction diode on a free-standing GaN substrate with a field-plate (FP) structure. We demonstrated reduced plasma damage during the sputtering process by cure annealing, and succeeded in improving the breakdown voltage (VB) to -550V with the FP, compared with VB of -200V without the FP. Ga2O3 is a suitable material for the FP because its dielectric constant is similar to that of GaN and it is more easily etched than Al2O3, which is used as a conventional insulator. DOI: 10.7567/JJAP.57.070302 Web of Science Scopus researchmap Study on the Main-Chain Structure of Amorphous Fluorine Resins for Encapsulating AlGaN-Based DUV-LEDs Yamada, K; Nagasawa, Y; Nagai, S; Hirano, A; Ippommatsu, M; Aosaki, K; Honda, Y; Amano, H; Akasaki, I PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE 215 巻 ( 10 ) 頁: 1700525 2018年5月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Physica Status Solidi (A) Applications and Materials Science The main chain structure of optically isotropic amorphous fluorine resin for encapsulating AlGaN-based deep-ultraviolet LEDs (λ < 300 nm) is studied. One type of amorphous fluorine resin has a five-membered ring with a single oxygen atom and the other has that one with two oxygen atoms. Reliability testing is performed using AlGaN-based LEDs of 262 and 289 nm. For the resin with two oxygen atoms in the ring, visible damage to the electrode and significantly increased leakage current are considered to been caused by the photolysis of the ring induced by irradiation with deep-ultraviolet light. In contrast, electrode damage and increased leakage are not observed in the case of the resin with the single-oxygen ring. DOI: 10.1002/pssa.201700525 Web of Science Scopus researchmap Insight into the performance of multi-color InGaN/GaN nanorod light emitting diodes Robin Y., Bae S. Y., Shubina T. V., Pristovsek M., Evropeitsev E. A., Kirilenko D. A., Davydov V. Yu., Smirnov A. N., Toropov A. A., Jmerik V. N., Kushimoto M., Nitta S., Ivanov S. V., Amano H. SCIENTIFIC REPORTS 8 巻 頁: 7311 2018年5月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1038/s41598-018-25473-x Web of Science m-Plane GaN Schottky Barrier Diodes Fabricated With MOVPE Layer on Several Off-Angle m-Plane GaN Substrates Tanaka, A; Ando, Y; Nagamatsu, K; Deki, M; Cheong, H; Ousmane, B; Kushimoto, M; Nitta, S; Honda, Y; Amano, H PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE 215 巻 ( 9 ) 頁: 1700645 2018年5月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Physica Status Solidi (A) Applications and Materials Science In this study, GaN m-plane Schottky barrier diodes are fabricated by metalorganic vapor-phase epitaxy (MOVPE) on several off-angle gallium nitride (GaN) substrates, and the off-cut angle dependence of impurity incorporation is investigated. We show that the MOVPE layer on the substrate inclined 5° toward the [000–1] direction has extremely low impurity incorporation. These results provide important suggestions for the fabrication of m-plane power devices. DOI: 10.1002/pssa.201700645 Web of Science Scopus researchmap Interface amorphization in hexagonal boron nitride films on sapphire substrate grown by metalorganic vapor phase epitaxy Yang Xu, Nitta Shugo, Pristovsek Markus, Liu Yuhuai, Nagamatsu Kentaro, Kushimoto Maki, Honda Yoshio, Amano Hiroshi APPLIED PHYSICS EXPRESS 11 巻 ( 5 ) 頁: 051002 2018年5月 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Applied Physics Express Hexagonal boron nitride (h-BN) films directly grown on c-plane sapphire substrates by pulsed-mode metalorganic vapor phase epitaxy exhibit an interlayer for growth temperatures above 1200 °C. Cross-sectional transmission electron microscopy shows that this interlayer is amorphous, while the crystalline h-BN layer above has a distinct orientational relationship with the sapphire substrate. Electron energy loss spectroscopy shows the energy-loss peaks of B and N in both the amorphous interlayer and the overlying crystalline h-BN layer, while Al and O signals are also seen in the amorphous interlayer. Thus, the interlayer forms during h-BN growth through the decomposition of the sapphire at elevated temperatures. DOI: 10.7567/APEX.11.051002 Web of Science Scopus researchmap Transferrable monolithic multicomponent system for near-ultraviolet optoelectronics Qin Chuan, Gao Xumin, Yuan Jialei, Shi Zheng, Jiang Yuan, Liu Yuhuai, Wang Yongjin, Amano Hiroshi APPLIED PHYSICS EXPRESS 11 巻 ( 5 ) 頁: 051201 2018年5月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Applied Physics Express A monolithic near-ultraviolet multicomponent system is implemented on a 0.8-mm-diameter suspended membrane by integrating a transmitter, waveguide, and receiver into a single chip. Two identical InGaN/Al0.10Ga0.90N multiple-quantum well (MQW) diodes are fabricated using the same process flow, which separately function as a transmitter and receiver. There is a spectral overlap between the emission and detection spectra of the MQW diodes. Therefore, the receiver can respond to changes in the emission of the transmitter. The multicomponent system is mechanically transferred from silicon, and the wire-bonded transmitter on glass experimentally demonstrates spatial light transmission at 200 Mbps using non-return-to-zero on–off keying modulation. DOI: 10.7567/APEX.11.051201 Web of Science Scopus researchmap Correlation between dislocations and leakage current of p-n diodes on a free-standing GaN substrate Usami Shigeyoshi, Ando Yuto, Tanaka Atsushi, Nagamatsu Kentaro, Deki Manato, Kushimoto Maki, Nitta Shugo, Honda Yoshio, Amano Hiroshi, Sugawara Yoshihiro, Yao Yong-Zhao, Ishikawa Yukari APPLIED PHYSICS LETTERS 112 巻 ( 18 ) 頁: 182106 2018年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Applied Physics Letters Dislocations that cause a reverse leakage current in vertical p-n diodes on a GaN free-standing substrate were investigated. Under a high reverse bias, dot-like leakage spots were observed using an emission microscope. Subsequent cathodoluminescence (CL) observations revealed that the leakage spots coincided with part of the CL dark spots, indicating that some types of dislocation cause reverse leakage. When etch pits were formed on the dislocations by KOH etching, three sizes of etch pits were obtained (large, medium, and small). Among these etch pits, only the medium pits coincided with leakage spots. Additionally, transmission electron microscopy observations revealed that pure screw dislocations are present under the leakage spots. The results revealed that 1c pure screw dislocations are related to the reverse leakage in vertical p-n diodes. DOI: 10.1063/1.5024704 Web of Science Scopus researchmap Light output performance of red AlGaInP-based light emitting diodes with different chip geometries and structures Oh Jeong-Tak, Lee Sang-Youl, Moon Yong-Tae, Moon Ji Hyung, Park Sunwoo, Hong Ki Yong, Song Ki Young, Oh Chan-Hyoung, Shim Jong-In, Jeong Hwan-Hee, Song June-O, Amano Hiroshi, Seong Tae-Yeon OPTICS EXPRESS 26 巻 ( 9 ) 頁: 11194-11200 2018年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1364/OE.26.011194 Web of Science The 2018 GaN power electronics roadmap Amano H., Baines Y., Beam E., Borga Matteo, Bouchet T., Chalker Paul R., Charles M., Chen Kevin J., Chowdhury Nadim, Chu Rongming, De Santi Carlo, De Souza Maria Merlyne, Decoutere Stefaan, Di Cioccio L., Eckardt Bernd, Egawa Takashi, Fay P., Freedsman Joseph J., Guido L., Haeberlen Oliver, Haynes Geoff, Heckel Thomas, Hemakumara Dilini, Houston Peter, Hu Jie, Hua Mengyuan, Huang Qingyun, Huang Alex, Jiang Sheng, Kawai H., Kinzer Dan, Kuball Martin, Kumar Ashwani, Lee Kean Boon, Li Xu, Marcon Denis, Maerz Martin, McCarthy R., Meneghesso Gaudenzio, Meneghini Matteo, Morvan E., Nakajima A., Narayanan E. M. S., Oliver Stephen, Palacios Tomas, Piedra Daniel, Plissonnier M., Reddy R., Sun Min, Thayne Iain, Torres A., Trivellin Nicola, Unni V., Uren Michael J., Van Hove Marleen, Wallis David J., Wang J., Xie J., Yagi S., Yang Shu, Youtsey C., Yu Ruiyang, Zanoni Enrico, Zeltner Stefan, Zhang Yuhao JOURNAL OF PHYSICS D-APPLIED PHYSICS 51 巻 ( 16 ) 頁: 163001 2018年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Journal of Physics D: Applied Physics DOI: 10.1088/1361-6463/aaaf9d Web of Science Scopus researchmap 昇温脱離法によるInGaN表面上のCs層の解析 鹿島 将央, 佐藤 大樹, 小泉 淳, 西谷 智博, 本田 善央, 天野 浩, 飯島 北斗, 目黒 多加志 応用物理学会学術講演会講演予稿集 2018.1 巻 ( 0 ) 頁: 1670 - 1670 2018年3月 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:公益社団法人 応用物理学会 DOI: 10.11470/jsapmeeting.2018.1.0_1670 CiNii Research Growth of hexagonal boron nitride on sapphire substrate by pulsed-mode metalorganic vapor phase epitaxy Yang Xu, Nitta Shugo, Nagamatsu Kentaro, Bae Si-Young, Lee Ho-Jun, Liu Yuhuai, Pristovsek Markus, Honda Yoshio, Amano Hiroshi JOURNAL OF CRYSTAL GROWTH 482 巻 ( 15 ) 頁: 1 - 8 2018年1月 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Journal of Crystal Growth Hexagonal boron nitride (h-BN) was directly grown on sapphire substrate using alternating ammonia (NH3) and triethylboron (TEB) supply (pulsed mode) in metalorganic vapor phase epitaxy. The best condition is when just enough NH3 is supplied to fully convert the TEB within one cycle. Excess NH3 caused islands on h-BN film surface while a lack of NH3 does not form h-BN at all. The epitaxial relationship between grown h-BN layer and c-plane sapphire was confirmed to be [0001]h-BN∥[0001]sapphire and [10-10]h-BN∥[11-20]sapphire. It is known that, compared to AlN, BN requires higher V/III ratios for good crystallinity, which due to severe gas-phase reactions is difficult to achieve using continuous supply. Thus using pulsed mode the FWHM of the symmetric (0002) diffraction was almost halved and the growth rate was several times faster. DOI: 10.1016/j.jcrysgro.2017.10.036 Web of Science Scopus researchmap Electrical and Thermal Analysis of Vertical GaN-on-GaN PN Diodes Yates, L; Pavlidis, G; Graham, S; Usami, S; Nagamatsu, K; Honda, Y; Amano, H PROCEEDINGS OF THE 17TH IEEE INTERSOCIETY CONFERENCE ON THERMAL AND THERMOMECHANICAL PHENOMENA IN ELECTRONIC SYSTEMS (ITHERM 2018) 頁: 831 - 837 2018年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Web of Science Theoretical Study of the Electronic Structure of Threading Edge Dislocations in GaN Nakano Takashi, Araidai Masaaki, Shiraishi Kenji, Tanaka Atsushi, Honda Yoshio, Amano Hiroshi GALLIUM NITRIDE AND SILICON CARBIDE POWER TECHNOLOGIES 8 86 巻 ( 12 ) 頁: 41 - 49 2018年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:ECS Transactions It is very important to fabricate high-quality GaN especially used for power devices. However, threading dislocations degrade the performance of GaN-based electronic devices. It is necessary to examine the electronic behavior at threading dislocations in GaN and to clarify the origin of the leakage current. As for theoretical studies, the electronic structure of threading dislocations in GaN is not fully understood. We investigated whether threading edge dislocations contribute to the leakage current or not. To do this, we used first principles calculations based on density functional theory (DFT) to examine the electronic structure at threading edge dislocations with Burgers vectors of 1/3[11-20]. We examined four core types of atomic structure at threading edge dislocations which contains about 200 atoms. Compared with dislocation line energies of each core configurations, it was found that the 5/7-atoms ring core and 8-atoms ring core are energetically stable. Then, we analyzed the electronic densities of states of each core configurations, and it was found that all types of core configurations at threading edge dislocations do not contribute to leakage current in n-type GaN-based devices. DOI: 10.1149/08612.0041ecst Web of Science Scopus DFT modeling of carbon incorporation in GaN(0001) and GaN(000(1)over-bar) metalorganic vapor phase epitaxy 査読有り Pawel Kempisty, Yoshihiro Kangawa, Akira Kusaba, Kenji Shiraishi, Stanislaw Krukowski, Michal Bockowski, Koichi Kakimoto, and Hiroshi Amano APPLIED PHYSICS LETTERS 111 巻 頁: 141602/1-5 2017年10月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) The carbon incorporation mechanism in GaN(0001) and GaN(000 (1) over bar) during MOVPE was investigated using density functional theory (DFT) calculations. The results confirm that the crucial factors for carbon incorporation are Fermi level pinning and accompanying surface band bending. In addition, the lattice symmetry has a strong dependence on the stability of carbon in a few subsurface layers, which results from interactions between the impurities and surface states. It was shown that these effects are responsible for facilitating or hindering the incorporation of impurities and dopants. The influence of diluent gas species (hydrogen or nitrogen) on carbon incorporation was discussed. DOI: 10.1063/1.4991608 Initial leakage current paths in the vertical-type GaN-on-GaN Schottky barrier diodes Liwen Sang, Bing Ren, Masatomo Sumiya, Meiyong Liao, Yasuo Koide, Atsushi Tanaka, Yujin Cho, Yoshitomo Harada, Toshihide Nabatame, Takashi Sekiguchi, Shigeyoshi Usami, Yoshio Honda, and Hiroshi Amano APPLIED PHYSICS LETTERS 111 巻 頁: 122102/1-5 2017年9月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Electrical characteristics of leakage current paths in vertical-type n-GaN Schottky barrier diodes (SBDs) on free-standing GaN substrates are investigated by using photon emission microscopy (PEM). The PEM mapping shows that the initial failure of the SBD devices at low voltages is due to the leakage current paths from polygonal pits in the GaN epilayers. It is observed that these polygonal pits originate from carbon impurity accumulation to the dislocations with a screw-type component by microstructure analysis. For the SBD without polygonal pits, no initial failure is observed and the first leakage appeals at the edge of electrodes as a result of electric field concentration. The mechanism of leakage at pits is explained in terms of trap assisted tunneling through fitting current-voltage characteristics. DOI: 10.1063/1.4994627 Absolute technique for measuring internal electric fields in InGaN/GaN light-emitting diodes by electroreflectance applicable to all crystal orientations 査読有り Tomoyuki Tanikawa, Kanako Shojiki, Ryuji Katayama, Shigeyuki Kuboya, Takashi Matsuoka, Yoshio Honda, and Hiroshi Amano Applied Physics Express 10 巻 頁: 082101/1-4 2017年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.7567/APEX.10.082101 Low cost high voltage GaN polarization superjunction field effect transistors Kawai H., Yagi S., Hirata S., Nakamura F., Saito T., Kamiyama Y., Yamamoto M., Amano H., Unni V., Narayanan E. M. S. PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE 214 巻 ( 8 ) 頁: 1600834/1-10 2017年8月 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Physica Status Solidi (A) Applications and Materials Science A comprehensive overview of the novel high voltage GaN field effect transistors (FETs) based on the Polarization Superjunction (PSJ) concept, and a cost-effective approach towards manufacturing these high performance devices are presented. Current challenges impeding wider adoption of GaN power switching transistors in applications, and the latest results of the scaled-up PSJ-FETs from POWDEC KK, are also discussed. The article also presents hard-switching characteristics of 400–800 V boost converter, constructed using a PSJ-FET grown on sapphire substrate, and the future direction of GaN power semiconductor technology based on monolithic integration for advanced power electronics. DOI: 10.1002/pssa.201600834 Web of Science Scopus researchmap Facet dependence of leakage current and carrier concentration in m-plane GaN Schottky barrier diode fabricated with MOVPE 査読有り Atsushi Tanaka, Ousmane1 Barry, Kentaro Nagamatsu, Junya Matsushita, Manato Deki, Yuto Ando, Maki Kushimoto, Shugo Nitta, Yoshio Honda, and Hiroshi Amano Phys. Status Solidi A 214 巻 ( 8 ) 頁: 1600829/1-5 2017年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) In this study, GaN m-plane Schottky barrier diodes fabricated with a metalorganic vapor-phase epitaxy on a GaN substrate were investigated using emission microscope, photoluminescence, and cathodoluminescence. In addition, facet dependence of leakage current under reverse-biased condition was observed. We showed that the leakage-current distribution was caused by the facet dependence of the carrier concentration and oxygen concentration. These results can provide important suggestions for the fabrication of m-plane devices. (a) four-faceted hillocks on m-plane GaN MOVPE sample, facet dependence of (b) leakage current and (c) PL peak intensity of the m-plane GaN Schottky barrier diode. DOI: 10.1002/pssa.201600829 Effect of dislocations on the growth of p-type GaN and on the characteristics of p–n diodes 招待有り 査読有り 214 巻 ( 8 ) 頁: 1600837/1-5 2017年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1002/pssb.201600722 Selective-area growth of doped GaN nanorods by pulsed-mode MOCVD: Effect of Si and Mg dopants 査読有り Si-Young Bae, Kaddour Lekhal, Ho-Jun Lee, Jung-Wook Min, Dong-Seon Lee, Yoshio Honda, and Hiroshi Amano Phys. Status Solidi B 254 巻 ( 8 ) 頁: 1600722/1-7 2017年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Injecting current with a uniform carrier concentration is important for applications with three-dimensional architectures such as vertical power devices or displays. In III-nitride nanostructures, dopants not only incorporate differently depending on the surface orientation but can also seriously affect the kinetic equilibrium shapes of the nanorods. Herein, we report selective-area growth of doped GaN nanorods grown by pulsed-mode metalorganic chemical vapor deposition. Two dopants, Si and Mg, were employed as donor and acceptor atoms, respectively, for a mono-doping approach. Furthermore, a mixed flow of Si and Mg was supplied for a co-doping approach. We compared the morphological effects and growth rates of each doped GaN nanorod array. Then, we proposed appropriate growth mechanisms for the doped GaN nanorods on the basis of our structural characterizations. These results might extend the morphological functionality of GaN nanorods by including doping and may also provide an appropriate foundation for the design of nanostructure-based electronic or photonic devices. DOI: 10.1002/pssb.201600722 Decomposition of trimethylgallium and adduct formation in a metalorganic vapor phase epitaxy reactor analyzed by high-resolution gas monitoring system 査読有り Kentaro Nagamatsu, Shugo Nitta, Zheng Ye, Hirofumi Nagao, Shinichi Miki, Yoshio Honda, and Hiroshi Amano Phys. Status Solidi B 254 巻 ( 8 ) 頁: 1600737/1-4 2017年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1002/pssb.201600737 Effect of dislocations on the growth of p-type GaN and on the characteristics of p-n diodes Usami Shigeyoshi, Miyagoshi Ryosuke, Tanaka Atsushi, Nagamatsu Kentaro, Kushimoto Maki, Deki Manato, Nitta Shugo, Honda Yoshio, Amano Hiroshi PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE 214 巻 ( 8 ) 2017年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Physica Status Solidi (A) Applications and Materials Science We investigate the influence of crystal defects on p-type GaN grown by metalorganic vapor phase epitaxy. Sets of p-type GaN films were grown on sapphire substrates and on free-standing GaN (F-GaN) substrates simultaneously using various Et-Cp2Mg flow rates. Although there is a difference of two orders of magnitude between the threading dislocation densities of p-type GaN grown on sapphire and F-GaN substrates, there is no significant difference in hole concentration. However, there are problems with the surface morphology of p-type GaN grown on sapphire. The deterioration of the surface was caused by the difference in nanopipe density. The electrical properties of a p–n junction diode formed on sapphire with a high density of nanopipes were observed using emission microscopy under both forward- and reverse-bias conditions. Our results demonstrate that the nanopipes are electrically inactive, and that other types of threading dislocation have more influence on the current–voltage characteristics. DOI: 10.1002/pssa.201600837 Web of Science Scopus Role of threading dislocations in strain relaxation during GaInN growth monitored by real-time X-ray reflectivity 査読有り Guangxu Ju, Masao Tabuchi, Yoshikazu Takeda, and Hiroshi Amano Applied Physics Letters 110 巻 ( 26 ) 頁: 262105/1-5 2017年6月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1063/1.4990687 A-plane GaN growth on (11-20) 4H-SiC substrate with an ultrathin interlayer 査読有り Zheng Sun, Peifeng Song, Shugo Nitta, Yoshio Honda, Hiroshi Amano Journal of Crystal Growth 468 巻 頁: 866-869 2017年6月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1016/j.jcrysgro.2017.01.31 Selective-area growth of vertically oriented GaN nanostructures with a hafnium pre-orienting layer 査読有り S.-Y.Bae, K. Lekhal, H.-J.Lee, T.Mitsunari, J.-W.Min, D.-S.Leed, M.Kushimoto, Y.Honda, H.Amano Journal of Crystal Growth 468 巻 頁: 110-113 2017年6月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1016/j.jcrysgro.2016.10.032 Orientation-controlled epitaxial lateral overgrowth of semipolar GaN on Si(001) with a directionally sputtered AlN buffer layer 査読有り Ho-Jun Lee, Si-Young Bae, Kaddour Lekhal, Akira Tamura, Takafumi Suzuki, Maki Kushimoto, Yoshio Honda, and Hiroshi Amano Journal of Crystal Growth 468 巻 頁: 547-551 2017年6月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1016/j.jcrysgro.2016.11.116 Effect of V/III ratio on the surface morphology and electrical properties of m–plane ( 101¯0 ) GaN homoepitaxial layers 査読有り 468 巻 頁: 552-556 2017年6月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We have investigated the effect of V/III ratio on the surface morphology, impurity concentration and electrical properties of m–plane (101¯0) Gallium Nitride (GaN) homoepitaxial layers. Four-sided pyramidal hillocks are observed on the nominally on-axis m–plane GaN films. Hillocks sizes relatively increase by increasing the V/III ratio. All facets of pyramidal hillocks exhibit well-defined step-terrace features. Secondary ion mass spectrometry depth profiles reveal that carbon impurities decrease by increasing the V/III ratio while the lowest oxygen content is found at an optimized V/III ratio of 900. Vertical Schottky barrier diodes fabricated on the m–GaN samples were characterized. Low leakage current densities of the order of 10−10 A/cm2 at −5 V are obtained at the optimum V/III ratio. Oxygen impurities and screw-component dislocations around hillocks are found to have more detrimental impact on the leakage current mechanism. DOI: 10.1016/j.jcrysgro.2016.12.012 Annealing effect on threading dislocations in a GaN grown on Si substrate 査読有り 468 巻 頁: 835-838 2017年6月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Effect of rapid thermal annealing (RTA) on crystal defects in a GaN layer grown on a (111)Si substrate was investigated by photoluminescence (PL) and transmission electron microscopy (TEM) analyses. The PL spectra suggested that the density of gallium vacancy is not changed by the heat treatment up to 700 °C. In the TEM specimen, we had dislocation half loops generated by off-axis propagation of the threading dislocation. We found that the half-loop of c-type dislocation shrinks/moves by a repetitive RTA at 600–700 °C. In contrast, we could find no remarkable changes in the a-type or a+c-type dislocations. DOI: 10.1016/j.jcrysgro.2017.01.001 A-plane GaN growth on (11-20) 4H-SiC substrate with an ultrathin interlayer Sun Zheng, Song Peifeng, Nitta Shugo, Honda Yoshio, Amano Hiroshi JOURNAL OF CRYSTAL GROWTH 468 巻 頁: 866 - 869 2017年6月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Journal of Crystal Growth A-plane GaN was attempted to be grown on (11-20) 4H-SiC bulk substrate without using a traditional thick buffer layer. By inducing TMAl treatment before the GaN growth step and using both a low pressure and V/III ratio, the interlayer thickness of the a-plane GaN/SiC was reduced to 1.7+0.5 nm. The ultrathin interlayer was observed to be either AlN or AlGaN with a low Ga composition. This study is aimed to contribute to the understanding of GaN growth on the sidewalls of c-plane trench structure SiC. The ultrathin growth technique is also hoped to be applied to the fabrication of GaN-based vertical structure nonpolar optical or electrical devices. DOI: 10.1016/j.jcrysgro.2017.01.031 Web of Science Scopus Uneven AlGaN multiple quantum well for deep-ultraviolet LEDs grown on macrosteps and impact on electroluminescence spectral output 査読有り Michiko Kaneda, Cyril Pernot, Yosuke Nagasawa, Akira Hirano, Masamichi Ippommatsu, Yoshio Honda, Hiroshi Amano, and Isamu Akasaki Japanese Journal of Applied Physics 56 巻 頁: 061002 2017年5月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.7567/JJAP.56.061002 III-nitride core-shell nanorod array on quartz substrates Bae Si-Young, Min Jung-Wook, Hwang Hyeong-Yong, Lekhal Kaddour, Lee Ho-Jun, Jho Young-Dahl, Lee Dong-Seon, Lee Yong-Tak, Ikarashi Nobuyuki, Honda Yoshio, Amano Hiroshi SCIENTIFIC REPORTS 7 巻 頁: 45345 2017年3月 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Scientific Reports DOI: 10.1038/srep45345 Web of Science Scopus PubMed researchmap 紫外発光素子に向けたp層側光吸収低減の検討 安田 俊輝, 桑原 奈津子, 竹内 哲也, 岩谷 素顕, 上山 智, 赤﨑 勇, 天野 浩 応用物理学会学術講演会講演予稿集 2017.1 巻 ( 0 ) 頁: 3400 - 3400 2017年3月 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:公益社団法人 応用物理学会 DOI: 10.11470/jsapmeeting.2017.1.0_3400 CiNii Research NEA-InGaNフォトカソードの量子効率に対する熱処理の効果 鹿島 将央, 飯島 北斗, 西谷 智博, 佐藤 大樹, 本田 善央, 天野 浩, 目黒 多加志 応用物理学会学術講演会講演予稿集 2017.1 巻 ( 0 ) 頁: 1554 - 1554 2017年3月 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:公益社団法人 応用物理学会 DOI: 10.11470/jsapmeeting.2017.1.0_1554 CiNii Research フッ素系樹脂の深紫外発光ダイオード用封止樹脂としての耐久性とその劣化機構 長澤 陽祐, 山田 貴穂, 永井 祥子, 平野 光, 一本松 正道, 青崎 耕, 本田 善央, 天野 浩, 赤﨑 勇 応用物理学会学術講演会講演予稿集 2017.1 巻 ( 0 ) 頁: 1136 - 1136 2017年3月 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:公益社団法人 応用物理学会 DOI: 10.11470/jsapmeeting.2017.1.0_1136 CiNii Research Relationship between lattice relaxation and electrical properties in polarization doping of graded AlGaN with high AlN mole fraction on AlGaN template Yasuda Toshiki, Takeuchi Tetsuya, Iwaya Motoaki, Kamiyama Satoshi, Akasaki Isamu, Amano Hiroshi APPLIED PHYSICS EXPRESS 10 巻 ( 2 ) 2017年2月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Applied Physics Express We investigated polarization doping for hole generation in abrupt and graded GaN/Al0.7Ga0.3N interfaces on Al0.99Ga0.01N templates. The abrupt interface exhibited hole generation, whereas the graded interface exhibited electron generation. In the graded AlxGa1%xN (x = 0.65-0), a graded part with an AlN mole fraction ranging from 0.2 to 0 showed a large relaxation. Theoretical estimation revealed that this part contained positive polarization charges, accumulating electrons. Via Mg doping in the graded AlGaN layer, we obtained a high hole concentration of 3 &#39; 1013cm%2. These results indicate that understanding the relaxation conditions in the graded layer is indispensable for polarization doping. DOI: 10.7567/APEX.10.025502 Web of Science Scopus Relationship between lattice relaxation and electrical properties in polarization doping of graded AlGaN with high AlN mole fraction on AlGaN template 査読有り Toshiki Yasuda, Tetsuya Takeuchi, Motoaki Iwaya, Satoshi Kamiyama, Isamu Akasaki and Hiroshi Amano Applied Physics Express 10 巻 頁: 025502 2017年1月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: https://doi.org/10.4567/APEX.10.025502 From the dawn of gan-based light-emitting devices to the present day Amano H. Handbook of Solid-State Lighting and LEDs 頁: 3-12 2017年1月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1201/9781315151595 Scopus High quality Al0.99Ga0.01N layers on sapphire substrates grown at 1150 degrees C by metalorganic vapor phase epitaxy Katsuno Shota, Yasuda Toshiki, Hagiwara Koudai, Koide Norikatsu, Iwaya Motoaki, Takeuchi Tetsuya, Kamiyama Satoshi, Akasaki Isamu, Amano Hiroshi JAPANESE JOURNAL OF APPLIED PHYSICS 56 巻 ( 1 ) 2017年1月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.7567/JJAP.56.015504 Web of Science Reduction of Dislocations in GaN on Silicon Substrate Using In Situ Etching 査読有り Koji Matsumoto, Toshiaki Ono, Yoshio Honda, Tetsuya Yamamoto, Shigeyoshi Usami, Maki Kushimoto, Satoshi Murakami, and Hiroshi Amano Physica Status Solidi b 253 巻 頁: 1700387(1-7) 2017年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) A gallium nitride (GaN) epitaxial layer with a low density of threading dislocations is successfully grown on a silicon substrate by using in situ gasetching. Silicon nitride (SiNx) film is used as a mask, and ammonia is intermittently supplied in hydrogen ambient during the etching. After etching,high-density deep pits appeared on the surface of a GaN template layer and corresponded to the threading dislocations in the layer. In this novel method,before growing an additional GaN layer on the template GaN layer, a second SiNx layer is deposited after the etching process, and this layer prevents GaN nuclei from growing on the upper side-walls of the pits. By using this method, the density of threading dislocations of the GaN surface is reduced to 6.7E7 cm2. This method is cost effective, completing all the necessary processes in one growth run without taking samples out from a metalorganic chemical vapor deposition (MOCVD) reactor. DOI: 10.1002/pssb.201700387 Development of Sustainable Smart Society based on Transformative Electronics Ogura, M; Ando, Y; Usami, S; Nagamatsu, K; Kushimoto, M; Deki, M; Tanaka, A; Nitta, S; Honda, Y; Pristovsek, M; Kawai, H; Yagi, S; Amano, H 2017 IEEE INTERNATIONAL ELECTRON DEVICES MEETING (IEDM) 頁: . 2017年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Web of Science Progress and Prospect of Growth of Wide-Band-Gap Group III Nitrides Amano Hiroshi III-NITRIDE BASED LIGHT EMITTING DIODES AND APPLICATIONS, 2ND EDITION 133 巻 頁: 1 - 9 2017年 詳細を見る 記述言語:日本語 掲載種別:研究論文(学術雑誌) 出版者・発行元:Topics in Applied Physics DOI: 10.1007/978-981-10-3755-9_1 Web of Science Scopus researchmap From the Dawn of GaN-Based Light-Emitting Devices to the Present Day Amano, H HANDBOOK OF SOLID-STATE LIGHTING AND LEDS 頁: 3 - 11 2017年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Web of Science High quality Al0.99Ga0.01N layers on sapphire substrates grown at 1150 °C by metalorganic vapor phase epitaxy 査読有り Shota Katsuno, Toshiki Yasuda, Koudai Hagiwara, Norikatsu Koide, Motoaki Iwaya, Tetsuya Takeuchi, Satoshi Kamiyama, Isamu Akasaki, and Hiroshi Amano Japanese Journal of Applied Physics 56 巻 頁: 015504 2016年12月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: https://doi.org/10.7567/JJAP.56.015504 Improved crystal quality of semipolar (10(1)over-bar3) GaN on Si(001) substrates using AlN/GaN superlattice interlayer 査読有り Ho-Jun Lee, Si-Young Bae, Kaddour Lekhal, Tadashi Mitsunaria, Akira Tamura, Yoshio Honda, Hiroshi Amano Journal of Crystal Growth 454 巻 頁: 114-120 2016年11月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: https://doi.org/10.1016/j.jcrysgro.2016.09.004 Controlled morphology of regular GaN microrod arrays by selective area growth with HVPE 査読有り Kaddour Lekhal, Si-Young Bae, Ho-Jun Lee, Tadashi Mitsunari, Akira Tamura, Manato Deki, Yoshio Honda, Hiroshi Amano Journal of Crystal Growth 447 巻 頁: 55-61 2016年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) The selective area growth (SAG) of GaN was implemented on patterned GaN/sapphire templates by hydride vapor phase epitaxy (HVPE) to fabricate regular arrays of Ga-polar GaN microrods. The control of growth parameters such as H2/N2 carrier gas ratio, growth temperature, and absolute NH3/HCl gas flow resulted in changes in the growth morphology. DOI: 10.1016/j.jcrysgro.2016.05.008 Development of highly durable deep-ultraviolet AlGaN-based LED multichip array with hemispherical encapsulated structures using a selected resin through a detailed feasibility study 査読有り Shoko Nagai, Kiho Yamada, Akira Hirano, Masamichi Ippommatsu, Masahiro Ito, Naoki Morishima, Ko Aosaki, Yoshio Honda, Hiroshi Amano, and Isamu Akasaki Japanese Journal of Applied Physics 55 巻 頁: 082101/1-7 2016年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: http://doi.org/10.7567/JJAP.55.082101 Deep level study of Mg-doped GaN using deep level transient spectroscopy and minority carrier transient spectroscopy 査読有り Tran Thien Duc, Galia Pozina, Hiroshi Amano, Bo Monemar, Erik Janz´en, and Carl Hemmingsson PHYSICAL REVIEW B94 巻 頁: 045206/1-8 2016年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Deep levels in Mg-doped GaN grown by metal organic chemical vapor deposition, undoped GaN grown by MOCVD, and halide vapor phase epitaxy-grown GaN have been studied using deep level transient spectroscopy and minority charge carrier transient spectroscopy. DOI: 10.1103/PhysRevB.94.045206 Study of radiation detection properties of GaN pn diode 査読有り Mutsuhito Sugiura, Maki Kushimoto, Tadashi Mitsunari, Kohei Yamashita, Yoshio Honda, Hiroshi Amano, Yoku Inoue, Hidenori Mimura, Toru Aoki, and Takayuki Nakano Japanese Journal of Applied Physics 55 巻 頁: 05FJ02/1-3 2016年5月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Recently, GaN, which has remarkable properties as a material for optical devices and high power electron devices, has also attracted attention as a material for radiation detectors. We previously suggested the use of BGaN as a neutron detector material. However, the radiation detection characteristics of GaN itself are not yet adequately understood. For realizing a BGaN neutron detector, the understanding of the radiation detection characteristics of GaN, which is a base material of the neutron detector, is important. In this study, we evaluated the radiation detection characteristics of GaN. We performed I V and energy spectrum measurements under alpha ray, gamma ray, and thermal neutron irradiations to characterize the radiation detection characteristics of a GaN diode. The obtained results indicate that GaN is an effective material for our proposed new BGaN-based neutron detector. Low-ohmic-contact-resistance V-based electrode for n-type AlGaN with high AlN molar fraction 査読有り Kazuki Mori, Kunihiro Takeda, Toshiki Kusafuka, Motoaki Iwaya, Tetsuya Takeuchi, Satoshi Kamiyama, Isamu Akasaki and Hiroshi Amano Low-ohmic-contact-resistance V-based electrode for n-type AlGaN with high AlN molar fraction 55 巻 ( 5S ) 頁: 05FL03/1-5 2016年5月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Observation of relaxation time of surface charge limit for InGaN photocathodes with negative electron affinity 査読有り Daiki Sato, Tomohiro Nishitani, Yoshio Honda and Hiroshi Amano Japanese Journal of Applied Physics 55 巻 ( 5S ) 頁: 05FH05/1-4 2016年5月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Emission Characteristics of InGaN/GaN Core-Shell Nanorods Embedded in a 3D Light-Emitting Diode 査読有り Byung Oh Jung, Si-Young Bae, Seunga Lee, Sang Yun Kim, Jeong Yong Lee, Yoshio Honda and Hiroshi Amano Nanoscale Research Letters 11 巻 2016年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We report the selective-area growth of a gallium nitride (GaN)-nanorod-based InGaN/GaN multiple-quantum-well (MQW) core-shell structure embedded in a three-dimensional (3D) light-emitting diode (LED) grown by metalorganic chemical vapor deposition (MOCVD) and its optical analysis. High-resolution transmission electron microscopy (HR-TEM) observation revealed the high quality of the GaN nanorods and the position dependence of the structural properties of the InGaN/GaN MQWs on multiple facets. The excitation and temperature dependences of photoluminescence (PL) revealed the m-plane emission behaviors of the InGaN/GaN core-shell nanorods. The electroluminescence (EL) of the InGaN/GaN core-shell-nanorod-embedded 3D LED changed color from green to blue with increasing injection current. This phenomenon was mainly due to the energy gradient and deep localization of the indium in the selectively grown InGaN/GaN core-shell MQWs on the 3D architecture. DOI: 10.1186/s11671-016-1441-6 Preflow trimethylaluminum treatment effect on GaN growth on SiC with an ultrathin interlayer 査読有り Zheng Sun, Kentaro Nagamatsu, Marc Olsson, Peifeng Song, Manato Deki, Shugo Nitta, Yoshio Honda and Hiroshi Amano Japanese Journal of Applied Physics, 55 巻 ( 5S ) 頁: 05FB06/1-5 2016年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Growth of semipolar (1-101) high-indium-content InGaN quantum well using InGaN tilting layer on Si(001) 査読有り Maki Kushimoto, Yoshio Honda and Hiroshi Amano Japanese Journal of Applied Physics 55 巻 ( 5S ) 頁: 05FA10/1-4 2016年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Evaluation of excess In during metal organic vapor-phase epitaxy growth of InGaN by monitoring via in situ laser scattering 査読有り Tetsuya Yamamoto, Akira Tamura, Shigeyoshi Usami, Tadashi Mitsunari, Kentaro Nagamatsu, Shugo Nitta, Yoshio Honda and Hiroshi Amano Japanese Journal of Applied Physics 55 巻 ( 5S ) 頁: 05FD03/1-4 2016年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Using an in situ laser absorption and scattering method, the surface roughness and incorporation of In in InGaN layers grown by metal organic vapor-phase epitaxy (MOVPE) were monitored. Development of GaN-based blue LEDs and metalorganic vapor phase epitaxy of GaN and related materials 招待有り Hiroshi Amano Progress in Crystal Growth and Characterization of Materials 62 巻 頁: 126–135 2016年4月 詳細を見る 担当区分:筆頭著者 記述言語:英語 DOI: https://doi.org/10.1016/j.pcrysgrow.2016.04.006 Structural and optical study of core–shell InGaN layers of nanorod arrays with multiple stacks of InGaN/GaN superlattices for absorption of longer solar spectrum 査読有り 55 巻 ( 5S ) 頁: 05FG03/1-8 2016年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We report on the material and optical properties of core–shell InGaN layers grown on GaN nanorod arrays. The core–shell InGaN layers were well grown on polarization-reduced surfaces such as semipolar pyramids and nonpolar sidewalls. In addition, to compensate the biaxial strain between GaN and InGaN layers, we grew interlayers underneath a thick InGaN layer. Here, the interlayers were composed of multiple superlattice structures. We could observe that the indium composition of core–shell InGaN structures increased with the number of interlayers. This indicates that the absorption energy band of InGaN alloys can be better matched to the spectral irradiance of the solar spectrum in nature. We also implemented a simulation of Ga-polar and nonpolar InGaN-based solar cells based on the indium composition obtained from the experiments. The result showed that nonpolar InGaN solar cells had a much higher efficiency than Ga-polar InGaN solar cells with the same thickness of the absorption layer. Selective-area growth of GaN microrods on strain-induced templates by hydride vapor phase epitaxy 査読有り Kaddour Lekhal, Si-Young Bae, Ho-Jun Lee, Tadashi Mitsunari, Akira Tamura, Manato Deki, Yoshio Honda and Hiroshi Amano Japanese Journal of Applied Physics 55 巻 頁: 05FF03/1-5 2016年3月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Theoretical approach to surface reconstruction of InN(0001) during raised-pressure metalorganic vapor-phase epitaxy 査読有り Akira Kusaba, Yoshihiro Kangawa, Yoshio Honda, Hiroshi Amano and Koichi Kakimoto Japanese Journal of Applied Physics 55 巻 ( 5S ) 頁: 05FM01/1-4 2016年2月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Study of enhanced photovoltaic behavior in InGaN-based solar cells by using SiNx insertion layer: Influence of dislocations 査読有り Seunga Lee, Yoshio Honda, Hiroshi Amano, Jongjin Jang and Okhyun Nam Japanese Journal of Applied Physics Rapid Communications 55 巻 ( 3 ) 頁: 030306/1-4 2016年2月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Using a SiN insertion layer to reduce dislocations, enhanced photovoltaic properties could be obtained in pin InGaN GaN heterojunction solar cell. To investigate the influence of the dislocations on the photovoltaic behaviors, a sample grown without SiN insertion layer was identically prepared for comparison. From optical properties measurements, the reduction in the number of non-radiative centers and a stronger In localization effect was shown in the sample with SiN insertion layer. However, the quantum confined stark effect was almost negligible in both the samples. Effect of piezoelectric field on carrier dynamics in InGaN-based solar cells 査読有り Lee, Seunga; Honda, Yoshio; Amano, Hiroshi JOURNAL OF PHYSICS D-APPLIED PHYSICS 49 巻 ( 2 ) 頁: 025103 2016年1月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) To understand the effect of piezoelectric fields on carrier dynamics, we numerically investigated a simple p-GaN/i-InxGa1-xN/n-GaN solar cell structure. A reliable simulation model was obtained by comparing the experimental and simulated results in advance. Highly elongated vertical GaN nanorod arrays on Si substrates with an AlN seed layer by pulsed-mode metal-organic vapor deposition 査読有り Si-Young Bae, Byung Oh Jung, Kaddour Lekhal, Sang Yun Kim, Jeong Yong Lee, Dong-Seon Lee, Manato Deki, Yoshio Honda and Hiroshi Amano CrystEngComm 18 巻 頁: 1505-1514 2016年1月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) . Unlike the thick and high (or middle)-quality GaN templates normally used, nanorod growth was performed on an ultrathin and low-quality AlN/Si platform. Using kinetically controlled growth conditions and a patterning process, exceptionally long GaN nanorods were achieved with high geometric precision. DOI: 10.1039/C5CE02056E The interface analysis of GaN grown on 0° off 6H-SiC with an ultra-thin buffer layer 査読有り Zheng Sun, Akio Ohta, Seiichi Miyazaki, Kentaro Nagamatsu, Hojun Lee, Marc Olsson, Zheng Ye, Manato Deki, Yoshio Honda, and Hiroshi Amano Japanese Journal of Applied Physics 55 巻 頁: 010303/1-3 2016年1月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Previously, we reported a growth method by MOVPE using a single two-dimensional growth step, resulting in 1.2-micron thick crack-free GaN directly grown on 6H-SiC substrate. The introduction of Al-treatment prior to the standard GaN growth step resulted in improved surface wetting of gallium on the SiC substrate. Growth of GaN on sapphire via low-temperature deposited buffer layer and realization of p-type GaN by Mg doping followed by low-energy electron beam irradiation 招待有り 査読有り Hiroshi Amano Rev. Mod. Phys. 87 巻 ( 4 ) 頁: 1133-1138 2015年12月 詳細を見る 担当区分:筆頭著者 記述言語:英語 掲載種別:研究論文(学術雑誌) This is a personal history of one of the Japanese researchers engaged in developing a method forgrowing GaN on a sapphire substrate, paving the way for the realization of smart television anddisplay systems using blue LEDs. The most important work was done in the mid to late 1980s. Thebackground to the author&#39;s work and the process by which the technology enabling the growth ofGaN and the realization of p-type GaN was established are reviewed. Single-crystalline semipolar GaN on Si(001) using a directional sputtered AlN intermediate layer 査読有り Tadashi Mitsunari, Ho Jun Lee, Yoshio Honda, Hiroshi Amano Journal of Crystal Growth 431 巻 頁: 60-63 2015年12月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We obtained single-crystalline semipolar (10View the MathML source1¯3)GaN on a nominal Si(001) substrate with sputtered AlN using the directional feature of sputtering. DOI: 10.1016/j.jcrysgro.2015.08.027 Time-resolved photoluminescence properties of hybrids based on inorganic AlGaN/GaN quantum wells and colloidal ZnO nanocrystals 査読有り M. Forsberg, C. Hemmingsson, H. Amano, G. Pozina Superlattices and Microstructures 87 巻 頁: 38-41 2015年11月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Dynamic properties are studied for the AlGaN/GaN quantum well (QW) structures with and without the coating of colloidal ZnO nanocrystals (NCs). The QW exciton recombination rate was reduced in such hybrids compared to the bare QW structure only in the sample with the thinnest cap layer of 3 nm. Assuming that one of the recombination mechanisms in this hybrid is non-radiative resonant energy transfer (NRET) between the QW and the energy acceptor material i.e. ZnO NCs, the maximum pumping efficiency was estimated to be 0.42 at 60 K. The NRET effect is, however, vanished after several months despite that the hybrid structures are composed of chemically stable components. DOI: doi:10.1016/j.spmi.2015.07.017 Polarization dilution in a Ga-polar UV-LED to reduce the influence of polarization charges 査読有り Toshikiu Yasuda, Kento Hayashi, Syouta Katsuno, Tetsuya Takeuchi, Satoshi Kamiyama, Motoaki Iwaya, Isamu Akasaki, and Hiroshi Amano Physica Status Solidi a 212 巻 ( 5 ) 頁: 920-924 2015年5月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We investigated the influence of polarization charges in nitride-based semiconductors. DOI: 10.1002/pssa.201431730 Excitation density dependence of radiative and nonradiative recombination lifetimes in InGaN/GaN multiple quantum wells 査読有り Hideaki Murotani, Yoichi Yamada, Yoshio Honda, and Hiroshi Amano Physica Status Solidi b 252 巻 ( 5 ) 頁: 940-945 2015年5月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) The optical properties of InGaN/GaN multiple quantum wells (MQWs) have been studied by means of photoluminescence (PL) and time-resolved photoluminescence (TRPL) spectroscopy. DOI: 10.1002/pssb.201451491 Resonant Raman and FTIR spectra of carbon doped GaN 査読有り S. Ito, H. Kobayashi, K. Arak,i, K. Suzuki, N. Sawaki, K. Yamashita, Y. HOnda, H. Amano Journal of Crystal Grwoth 414 巻 ( 15 ) 頁: 56-60 2015年3月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: doi:10.1016/j.jcrysgro.2014.11.024 Electrical characteristics of a-plane low-Mg-doped p-GaN Schottky contacts 査読有り Moe Naganawa, Toshichika Aoki, Ji-Su Son, Hiroshi Amano, Kenji Shiojima physica status solidi (b) 252 巻 ( 5 ) 頁: 1024–1030 2015年3月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Electrical characteristics of a variety of Schottky contacts formed with ten metal species on the a-plane of p-type low-Mg-doped GaN grown on r-plane sapphire substrates were studied. DOI: 10.1002/pssb.201451581 Optically pumped lasing properties of (1-101) InGaN/GaN stripe multi quantum wells with ridge cavity structure on patterned (001) Si substrates 査読有り Maki Kushimoto, Tomoyuki Tanikawa, Yoshio Honda and Hiroshi Amano Applied Physics Express 8 巻 ( 2 ) 頁: 022702 2015年2月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We demonstrated lasing action and investigated the optical properties of (1 (1) over bar 01) multiquantum-well (MQW) stripe crystals on patterned (001) Si substrates. Longitudinal and higher order transverse modes were observed from a ridge waveguide structure. These results strongly suggest the possibility of fabricating (1 (1) over bar 01) InGaN MQW laser diodes on (001) Si. (C) 2015 The Japan Society of Applied Physics DOI: doi:10.7567/APEX.8.022702 Dynamic properties of excitons in ZnO/AlGaN/GaN hybrid nanostructures 査読有り Mathias Forsberg, Carl Hemmingsson, Hiroshi Amano , Galia Pozina Scientific Reports 5 巻 頁: 7889 2015年1月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) III-nitride semiconductor/organic polymer hybrid heterostructures combine advantages of epitaxially grown semiconductor quantum wells (QW) with inexpensive polymers having efficient luminescence in the visible region1. Such hybrid micro-structured light emitting diodes (LED) are promising for fabrication of low-cost and highly efficient microlight sources that can be used in full-color displays, imaging systems, miniature chemical and biological sensors. In typical polyfluorene/GaN-based LED hybrids, UV emission from a GaN heterostructure down converts to the organic polymer fluorescence in the visible region via a radiative energy transfer. Overlapping between the UV luminescence and the polyfluorene absorption is required for the operationof these hybrids. Today, a novel class of hybrid structures is suggested, in which a non-radiative resonant energy transfer (NRET) from excitation generated in inorganic QWs to excitons in organic films can be utilized. Such LEDs might be considerably more efficient than their radiative energy transfer analogues. In addition to the necessity of a significant spectral overlap between the QW emission and the polymer absorption spectrum, these devices require that the two materials are placed in a close interaction distance of a few nm. The bottleneck is that the operation lifetime of organic/semiconductor hybrid LED structures is limited by degradationof polyfluorenes. Using colloidal semiconductor nanocrystals (NCs) instead of polymers can significantly improve the lifetime of such devices. In addition to superior luminescence properties, relatively low cost and chemical stability, the spectral tunability can be achieved by changing the particle chemistry and size. The efficiency of non-radiative resonance energy transfer is typically determined using transient photoluminescence(PL) measurements from the quenching of the QW exciton lifetime in the presence of acceptor material (i.e.colloidal NCs or polyfluorene). It might be correct in assumption that NRET is the only additional recombination channel appearing in hybrids compared to the bareQWstructure. However, other factors can play also a significant role. For example, surface potential effects have to be considered when non-radiative resonant energy transfer is measured using dynamic properties of the QW excitons.Thus, in this work we have studied and discussed the possibility of NRET in hybrid structures fabricated using ZnO NCs films coated on the top of the AlGaN/GaN QWs samples. ZnO NCs satisfies the requirement ofabsorption overlapping with GaN emission (a room temperature band gap energy is 3.3 and 3.4 eV for ZnO and GaN, respectively). Dynamic properties ofQWexcitons in the hybrids and in the bareQWsamples are analyzed in dependence on the QWs cap layer thickness. DOI: doi:10.1038/srep07889 Development of underfilling and encapsulation for deep-ultraviolet LEDs 査読有り Kiho Yamada, Yuuta Furusawa, Shoko Nagai, Akira Hirano, Masamichi Ippommatsu, Ko Aosaki, Naoki Morishima, Hiroshi Amano and Isamu Akasaki Applied Physics Express 8 巻 ( 1 ) 頁: 012101 2015年1月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) The currently available resins for underfilling and encapsulation are limited to wavelengths longer than approximately 330 nm because almost all resins are decomposed by deep-ultraviolet light. Fluorine resins are possible materials for underfilling and encapsulation in deep-ultraviolet LEDs, and we have investigated methods of underfilling and encapsulation using such resins. Also, their durability at wavelengths of 265 and 285 nm has been studied from the photochemical viewpoint, and we propose a stable amorphous fluorine resin that is optically isotropic. Also, a trial of encapsulation using the resin has been made. DOI: doi:10.7567/APEX.8.012101 Highly ordered catalyst-free InGaN/GaN core-shell architecture arrays with expanded active area region 査読有り Jung, Byung Oh; Bae Si-Young; Kim, Sang Yun; Lee, Seunga; Lee, Jeong Yong; Lee, Dong-Seon; Kato, Yoshihiro; Honda, Yoshio ;Amano, Hiroshi Nano Energy 11 巻 頁: 294-303 2015年1月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Highly ordered, position-controlled gallium nitride (GaN) nanowire based multiple-quantum-wells (MQWs) core-shell architecture arrays are synthesized by metalorganic chemical vapor deposition (MOCVD). We investigate the possibility of using GaN nanowire arrays as a basal template for the growth of InxGa1-xN/GaN MQWs. The MQWs on three different crystal facets (c(-), m(-), and semipolar-plane) of GaN nanowire exhibit dissimilar structural properties. The structural characteristics of InGaN/GaN core-shell arrays are inspected by cross-sectional high-resolution transmission electron microscopy (HR-TEM). We also investigate the optical properties of MQW core-shell structure nanoarrays. The luminescent characteristics of InGaN/GaN core-shell structure arrays are determined by photoluminescence (PL) and cathodoluminescence (CL) measurements. The monochromatic CL images clearly show the light emission behavior of InGaN/GaN MQW coaxial structure. Two distinguishable light emission peaks were observed in the GaN nanowire based core-shell structure. The characteristic of light emission mainly depends on the properties of MQWs, which are generated from different crystal facets of GaN. In addition, the light emission intensity shows different behaviors depending on the area of the GaN nanowire m-plane. The results of this study suggest that GaN nanowire arrays can be used as a good alternative basal template for next-generation light-emitting diodes (LEDs). DOI: DOI: 10.1016/j.nanoen.2014.11.003 Continuous in situ X-ray reflectivity investigation on epitaxial growth of InGaN by metalorganic vapor phase epitaxy 査読有り Guangxu Ju, Shingo Fuchi, Masao Tabuchi, Hiroshi Amano, Isamu Akasaki Journal of Crystal Growth 407 巻 頁: 68-73 2014年12月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Continuous in situ X-rayreflectivity(XRR)measurementswereusedtoinvestigatethegrowthprocessofan In0.11Ga0.89N epilayeranditssinglequantumwellgrownonc-planeGaN/sapphiretemplatesusinganin-house-designed metalorganicvaporphaseepitaxyinstalledinalaboratory-gradeX-raydiffract-ometer.Thesurfacerougheningoftheepilayerasafunctionofgrowthtimewascalculatedfromthecontinuous in situ XRR curve.Thegrowthrate,criticalthickness hc(r) for surfaceroughening,androughening ratewereobtained.Theexperimentalcriticalthickness hc(r) of theIn0.11Ga0.89N epilayeranalyzed fromthecontinuous in situ XRR curvewas14.870.4 nm.Basedonthecalculatedtheoreticalcritical thickness hc and theexperimental hc(r,2), Fischer&#39;s modelseemstobeappropriatefordescribingthe criticalthicknessoftheInGaN/GaN. DOI: 10.1016/j.jcrysgro.2014.08.023 Photoemission lifetime of a negative electron affinity gallium nitride photocathode 査読有り Tomohiro Nishitani, Masao Tabuchi, Hiroshi Amano, Takuya Maekawa, Makoto Kuwahara and Takashi Meguro Journal of Vacuum Science and Technology B32 巻 ( 6 ) 頁: 06F901 2014年11月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) A photocathode electron source using p-type GaN semiconductor with a negative electron affinity (NEA) surface has been studied for its ability to maintain an extended NEA state. The key technology of NEA photocathodes is the formation of electric dipoles by cesium and gallium atoms on the surface, which makes it possible for photoexcited electrons in the conduction band minimum to escape into the vacuum. This means that in order to keep the electron energy spread as small as possible, the excitation photon energy should be tuned to the band gap energy. However, the NEA surface is damaged by the adsorption of residual gas and the back-bombardment of ionized residual gas by photoelectrons. The p-type GaN semiconductor was measured time evolution in quantum yield during NEA surface activation, and a lifetime of quantum yield of excitation energy corresponding to the band gap energy in comparison to the p-type GaAs as the conventional NEA photocathode. In NEA surface activation process, the quantum yield of the GaN was more than 3 orders of magnitude higher than that of the GaAs by only cesium deposition. The exposure amount of cesium in the NEA surface activation of the GaAs was 1.5 times as that of the GaN, even though the quantum yield of the GaAs was the same value as the GaN. Lifetime of NEA-photocathodes using the GaN was 21 times longer than that using the GaAs. The decrease of quantum yield of the GaAs was well correlated in the form of the exponential decrease function with a decrease time of 4.4 h, while the decrease of quantum yield of the GaN was well correlated in the form of the exponential decrease function with two decrease times of 47 and 174 h. Nature of yellow luminescence band in GaN grown on Si substrate 査読有り Shogo Ito, Taihei Nakagita, Nobuhiko Sawaki, Hyung Soo Ahn, Masashi Irie, Toshiki Hikosaka, Yoshio Honda, Masahito Yamaguchi and Hiroshi Amano Japanese Journal of Applied Physics 53 巻 頁: 11RC02/1-5 2014年9月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: doi:10.7567/JJAP.53.11RC02 Atom probe tomography study of Mg-doped GaN layers 査読有り S Khromov, D Gregorius, R Schiller, J Lösch, M Wahl, M Kopnarski, H Amano, B Monemar, L Hultman and G Pozina Nanotechnology 25 巻 ( 27 ) 2014年6月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: doi:10.1088/0957-4484/25/27/275701 Characterization of nonpolar a-plane InGaN/GaN multiple quantum well 査読有り Ji-Su Son, Yoshio Honda, Masahito Yamaguchi and Hiroshi Amano Japanese Journal of Applied Physics 53 巻 頁: 05FL01 2014年5月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) The characteristics of nonpolar a-plane (1120) GaN (a-GaN) grown using single and double nanopillar SiO2 masks were investigated. The twonanopillar SiO2 masks were directly fabricated on an r-plane sapphire substrate and a-GaN by the epitaxial lateral overgrowth (ELOG) technique.Through the use of the single and double nanopillar SiO2 masks, the crystalline quality and optical properties of a-GaN were markedly improvedbecause of the nanoscale ELOG effect and a number of voids in the single and double nanopillar SiO2 mask areas in comparison with the planarsample. The submicron pit densities of the planar, single, and double nanopillar mask samples were >2 &#39; e9, >7e8, and >4e8cm-2,respectively. The internal quantum efficiency (IQE) values at room temperature of three-period InGaN/GaN multiple quantum wells (MQWs) grownusing the planar, single, and double nanopillar masks were 45, 60, and 68% at a carrier concentration of 1.0e18cm-3, respectively. DOI: 10.7567/JJAP.53.05FL01 X-ray investigations of GaInN single quantum wells grown by atomic layer epitaxy and metalorganic vapor phase epitaxy 査読有り Guangxu Ju, Yoshihiro Kato, Yoshio Honda, Masao Tabuchi, Yoshikazu Takeda, and Hiroshi Amano physica status solidi (c) 11 巻 ( 3-4 ) 頁: 393-396 2014年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) A set of GaN/GaInN single quantum wells (SQWs) were grown on c-plane GaN/sapphire templates using metal organic vapor phase epitaxy (MOVPE) and atomic layer epitaxy (ALE). The structural information on the interfaces and surfaces was obtained by fitting the experimental X-ray spectra and was compared between MOVPE and ALE mode. The X-ray crystal truncation rod (CTR) scattering measurement results showed that the samples grown by ALE had sharper interfaces than those grown by MOVPE. Both the X-ray reflectivity (XRR) curve-fitting results and atomic force microscope (AFM) results indicated that the surfaces of the ALE-grown SQWs were smoother than those of MOVPE-grown SQWs. DOI: 10.1002/pssc.201300670 Enhancement of light output power on GaN based light emitting diodes using two direction stripe patterned sapphire substrate 査読有り Okuno, Koji; Oshio, Takahide; Shibata, Naoki; Honda, Yoshio; Yamaguchi, Masahito; Amano, Hiroshi Physica Status Solidi C 11 巻 頁: 722-725 2014年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) To achieve both the reduction of threading dislocation density (TDD) and the enhancement of light extraction efficiency (LEE) of light-emitting diodes (LEDs), a two-directional stripe-patterned sapphire substrate (TPSS) was fabricated. First, a stripe pattern parallel to the a-axis of Al2O3 was formed on an as-received c -sapphire wafer and then a second stripe pattern rotated around 3° from the m-axis of Al2O3 was formed on the first stripe PSS. The light output power of TPSS LEDs was around 1.25 times higher than that of LEDs on a flat sapphire substrate. This enhancement is caused by the increase of both the internal quantum efficiency (IQE) and the LEE. On the other hand, although the LED on TPSS with the second stripe just parallel to the m-axis of Al2O3 showed a similar enhancement ratio of the light output power, the current leakage of this LED increased with the concentration of threading dislocations on the surface of LEDs. Stripes rotated 3° from the m-axis of Al2O3 changed the growth mode and realized GaN films with a smooth surface without pit formation. Therefore, the misalignment of the stripe from the m-axis of Al2O3 will become a new design parameter for realizing high-efficiency reliable LEDs. DOI: 10.1002/pssc.201300470 Epitaxial growth of GaN by REMOCVD in the downflow of a very high frequency(VHF) N2/H2 excited plasma 査読有り Yi Lu, Hiroki Kondo,Kenji Ishikawa,Osamu Oda,KeigoTakeda,Makoto Sekine, Hiroshi Amano,Masaru Hori Journal of Crystal Growth 391 巻 頁: 97-103 2014年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We found that this REMOCVD allowed the growth of epitaxial GaN films of the wurtzite structure of (0001) orientation on sapphire substrates with a high growth rate of 0.42 μm/h at a low temperature of 800 °C. The present REMOCVD is a promising method for GaN growth at relatively low temperature and without using costly ammonia gas. DOI: 10.1016/j.jcrysgro.2014.01.014 Growth of InGaN/GaN multiple quantum wells on size-controllable nanopyramid arrays 査読有り Cao Miao, Yoshio Honda, Masahito Yamaguchi and Hiroshi Amano Japanese Journal of Applied Physics 53 巻 頁: 0303060 2014年3月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Regularly distributed nanopyramid arrays with a highly uniform size were grown by selective-area growth. The nanopyramid size could be tuned by varying the growth time. Two emission peaks were observed from multiple quantum wells grown on the nanopyramids. The longer-wavelength peak originated from the apexes of pyramids with threefold symmetry. High-density stacking faults observed at these triangular apexes might be responsible for the higher indium incorporation. The formation of embedded voids inside the pyramids was explained by the different growth rates at the edge and center of the mask window caused by the low diffusion length. DOI: 10.7567/JJAP.53.030306 In situ X-ray investigation of changing barrier growth temperatures on InGaN single quantum wells in metal-organic vapor phase epitaxy 査読有り Guangxu Ju, Yoshio Honda, Masao Tabuchi, Yoshikazu Takeda, and Hiroshi Amano Journal of Applied Physics 115 巻 頁: 094906 2014年3月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) The effects of GaN quantum barriers with changing growth temperatures on the interfacialcharacteristics of GaN/InGaN single quantum well (SQW) grown on GaN templates by metalorganicvapour phase epitaxy were in situ investigated by X-ray crystal truncation rod (CTR) scattering andX-ray reflectivity measurements at growth temperature using a laboratory level X-ray diffractometer.Comparing the curve-fitting results of X-ray CTR scattering spectra obtained at growth temperaturewith that at room temperature, the InxGa1-xN with indium composition less than 0.11 was stabile ofthe indium distribution at the interface during the whole growth processes. DOI: 10.1063/1.4867640 Multijunction GaInN-based solar cells using a tunnel junction 査読有り Hironori Kurokawa, Mitsuru Kaga, Tomomi Goda, Motoaki Iwaya, Tetsuya Takeuchi, Satoshi Kamiyama, Isamu Akasaki and Hiroshi Amano Applied Physics Express 7 巻 ( 3 ) 頁: 034104 2014年3月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We fabricated and characterized a two-junction GaInN-based solar cell using a tunnel junction fabricated by crystal growth. This solar cell has two active layers with a differing bandgap energy corresponding to blue or green light. We confirmed that the open-circuit voltage (VOC) in this solar cell was increased by the series connection using the tunnel junction. The short-circuit current density, VOC, fill factor, and energy conversion efficiency of this solar cell were 0.28 mA/cm2, 3.0 V, 0.5, and 0.41%, respectively, under an air mass filter of 1.5 G at 1-sun irradiation and room temperature. DOI: 10.7567/APEX.7.034104 Novel activation process for Mg-implanted GaN 査読有り Shin Hashimoto, Takao Nakamura, Yoshio Honda, Hiroshi Amano Journal of Crystal Growth 388 巻 頁: 112-115 2014年2月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) A novel activation process for Mg-implanted GaN was demonstrated. As opposed to the conventional thermal annealing process, an H2/NH3 alternating supply annealing process achieved better optical activation, stronger near-ultraviolet luminescence and weaker yellow luminescence in the photoluminescence spectroscopy. After this process, small hexagonal hillocks were observed on the surface, which indicated that crystal regrowth was induced by this process, consisting of decomposition of GaN by H2 supplies and re-crystallization by NH3 supplies. It was revealed that the implanted Mg could easily be located at the activation site by means of crystal regrowth by this process. DOI: doi:10.1016/j.jcrysgro.2013.07.011 Properties of the main Mg-related acceptors in GaN from optical and structural studies 査読有り B. Monemar, P. P. Paskov, G. Pozina, C. Hemmingsson, J. P. Bergman, S. Khromov, V. N. Izyumskaya, V. Avrutin, X. Li, H. Morkoç, H. Amano, M. Iwaya, and I. Akasaki Journal of Applied Physics 115 巻 頁: 053507 2014年2月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) The luminescent properties of Mg-doped GaN have recently received particular attention, e.g., in thelight of new theoretical calculations, where the deep 2.9 eV luminescence band was suggested to bethe main optical signature of the substitutional MgGa acceptor, thus, having a rather large bindingenergy and a strong phonon coupling in optical transitions. We present new experimental data onhomoepitaxial Mg-doped layers, which together with the previous collection of data give animproved experimental picture of the various luminescence features in Mg-doped GaN. DOI: 10.1063/1.4862928 Growth of low-defect-density nonpolar a-plane GaN on r-plane sapphire using pulse NH3 interrupted etching 査読有り Ji-Su Son, Yoshio Honda, and Hiroshi Amano Optics Express 22 巻 ( 3 ) 頁: 3585-3592 2014年2月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Nonpolar a-plane (11-20) GaN (a-GaN) layers with low overall defect density and high crystalline quality were grown on r-plane sapphire substrates using etched a-GaN. The a-GaN layer was etched by pulse NH3 interrupted etching. DOI: 10.1364/OE.22.003585 Morphology development of GaN nanowires using a pulsed-mode MOCVD growth technique 査読有り Byung Oh Jung, Si-Young Bae, Yoshihiro Kato, Masataka Imura, Dong-Seon Lee, Yoshio Honda and Hiroshi Amano CrystEngComm 16 巻 頁: 2273-2282 2014年1月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) we demonstrate a scalable process for the precise position-controlled selective growth ofGaN nanowire arrays by metalorganic chemical vapor deposition (MOCVD) using a pulsed-mode growthtechnique. The location, orientation, length, and diameter of each GaN nanowire are controlled viapulsed-mode growth parameters such as growth temperature and precursor injection and interruptiondurations. DOI: 10.1039/c3ce42266f Characteristics of a-plane GaN films grown on optimized silicon-dioxide-patterned r-plane sapphire substrates 査読有り Ji-Su Son, Y. Honda, M. Yamaguchi, H. Amano, K. H. Baik, Y. G. Seo and S. M. Hwang Thin Solid Films 546 巻 ( 11 ) 頁: 108-113 2013年11月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We report on the characteristics of a-plane GaN films directly grown on optimized silicon-dioxide-patterned r-plane sapphire substrates. Various shapes and sizes of silicon dioxide patterns were considered with the aim of achieving fully coalescent a-plane GaN films with a smooth surface and high crystalline quality. The omega full widths at half maximum of the X-ray rocking curve values of optimized a-plane GaN films with regular hexagonal patterns of 1 micron window width and 6 micron mask width were measured to be 597 arcsec along the c-axis direction and 457 arcsec along the m-axis direction. Atomic force microscopy images revealed a significant reduction in the density of submicron pits in the mask region. Effects of exciton localization on internal quantum efficiency of InGaN nanowires 査読有り Hideaki Murotani, Yoichi Yamada, Takuya Tabata, Yoshio Honda, Masahito Yamaguchi and Hiroshi Amano Journal of Applied Physics 114 巻 頁: 153506 2013年10月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Internal quantum efficiency of InGaN nanowires grown by PA MBE was investigated in detail. DOI: 10.1063/1.4825124 Strain-Compensated Effect on the Growth of InGaN/AlGaN Multi-Quantum Well by Metalorganic Vapor Phase Epitaxy 査読有り Tomohiro Doi, Yoshio Honda, Masahito Yamaguchi, and Hiroshi Amano Jpn. J. Appl. Phys. 52 巻 ( 8 ) 頁: 08JB14 2013年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) InGaN/AlGaN multi-quantum wells (MQWs) were grown by metalorganic vapor phase epitaxy. The In composition of the InGaN well layer was found to increase with the tensile strain of the AlGaN barrier layer. The InGaN/AlGaN strain-compensated structure can be grown at a higher growth temperature than that of the InGaN/GaN MQW, which shows that the same emission wavelength and thus the density of the V-defects can be effectively suppressed. DOI: 10.7567/JJAP.52.08JB14 GaN Overgrowth on Thermally Etched Nanoporous GaN Template 査読有り Cao Miao, Yoshio Honda, Masahito Yamaguchi, and Hiroshi Amano Jpn. J. Appl. Phys. 52 巻 ( 8 ) 頁: 08JB03 2013年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) A thermal-etching process for fabricating nanoporous GaN templates in a metalorganic vapor phase epitaxy (MOVPE) reactor was proposed. Such nanoporous templates exhibited nearly complete strain relaxation and considerably increased photoluminescence (PL) intensity. The threading dislocation density (TDD) after overgrowth was reduced from 3 ×109 to 4 ×108 cm-2 for the template with poor quality, whereas little improvement was observed for the high-quality template (TDD, 4 ×108 cm-2). Multiple quantum wells (MQWs) grown on a nanoporous template fabricated from the high-quality GaN template were used to assess the effect on LED performance. The PL intensity of the sample with a nanoporous structure showed a twofold increase in PL intensity compared with the control sample. DOI: 10.7567/JJAP.52.08JB03 Growth of GaN on Si(111) Substrates via a Reactive-Sputter-Deposited AlN Intermediate Layer 査読有り Takaya Yamada, Tomoyuki Tanikawa, Yoshio Honda, Masahito Yamaguchi, and Hiroshi Amano Japanese Journal of Applied Physics 52 巻 頁: 08JB16 2013年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) GaN films were successfully grown on Si(111) substrates using a reactive-sputter-deposited AlN intermediate layer (sp-AlN) at 350 °C. Uniform GaN growth was obtained with the pre sputtering of a thin Al film before the deposition of sp-AlN. Atomic force microscopy (AFM) measurements revealed that the density of pits originating from the ends of mixed/screw-type dislocations is about 109 cm-2, which is much lower than that of GaN grown on a metalorganic vapor phase epitaxy (MOVPE) deposited AlN intermediate layer. The decrease in the pit density might have originated from the small number of initial nuclei of GaN. DOI: 10.7567/JJAP.52.08JB16 Fabrication of InGaN/GaN Multiple Quantum Wells on (1-101) GaN 査読有り Tomoyuki Tanikawa, Tomotaka Sano, Maki Kushimoto, Yoshio Honda, Masahito Yamaguchi, and Hiroshi Amano Jpn. J. Appl. Phys. 52 巻 ( 8 ) 頁: 08JC05 2013年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) InGaN/GaN multiple quantum wells (MQWs) on semipolar (1101) GaN microstripes on a Si substrate were fabricated and their optical properties were investigated. From cathodoluminescence (CL) analysis, strong CL emission was obtained in an MQW emitting at 433 nm. However, dark lines appeared in MQWs emitting at longer wavelengths. These dark lines are attributed to lattice relaxation and the generation of misfit dislocations and stacking faults in an MQW, resulting in nonradiative centers. The internal quantum efficiency (IQE) was estimated from excitation-power-dependent photoluminescence analysis. The (1101) InGaN/GaN MQW had a high IQE owing to the high crystalline quality of the underlying GaN and the reduced piezoelectric field. The IQE at a carrier concentration of 1×1018 cm-3 in a sample emitting at 490 nm was as high as 90%. The efficiency decreased in a sample with a higher indium content in the MQW due to the generation of misfit dislocations and stacking faults. DOI: 10.7567/JJAP.52.08JC05 Stacking Faults and Luminescence Property of InGaN Nanowires 査読有り Takuya Tabata, Jihyun Paek, Yoshio Honda, Masahito Yamaguchi, and Hiroshi Amano Jpn. J. Appl. Phys. 52 巻 ( 8 ) 頁: 08JE06 2013年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) InGaN nanowires (NWs) were grown on (111)Si substrate using radio-frequency plasma-assisted molecular beam epitaxy, and the density of the stacking faults (SFs) in the InGaN NWs was estimated. High-density SFs were observed in the scanning transmission electron microscopy (STEM) and transmission electron microscopy (TEM) images of the InGaN NWs, and a few zincblende layers appeared in the wurtzite structure. When growth temperature increased, the density of the SFs in the InGaN NW, the photoluminescence (PL) peak wavelength, and the full width at half maximum (FWHM) of PL spectra decreased, whereas the integrated PL intensity increased. These results suggest that a high growth temperature is effective for decreasing the density of SFs in InGaN NWs, and InGaN NWs grown at high temperature have strong PL luminescence due to the low In composition and the corresponding low SFs density. DOI: 10.7567/JJAP.52.08JE06 Effects of Nano- and Microscale SiO2 Masks on the Growth of a-Plane GaN Layers on r-Plane Sapphire 査読有り Ji-Su Son, Cao Miao, Yoshio Honda, Masahito Yamaguchi, Hiroshi Amano, Yong Gon Seo, Sung-Min Hwang, and Kwang Hyeon Baik Jpn. J. Appl. Phys. 52 巻 ( 8 ) 頁: 08JC04 2013年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We report on the combined effects of a-plane GaN layers on a nanoscale patterned insulator on an r-plane sapphire substrate and epitaxial lateral overgrowth (ELOG) techniques. The fully coalescent a-plane GaN layer using nano- and microscale SiO2 masks showed the formation of nano- and microscale voids on the masks, respectively. Atomic force microscopy (AFM) measurements revealed a surface roughness of 0.63 nm and a submicron pit density of 7.8 ×107 cm-2. Photoluminescence (PL) intensity was enhanced by a factor of 9.0 in comparison with that of a planar sample. Omega full-width at half-maximum (FWHM) values of the (1120) X-ray rocking curve along the c- and m-axes were 553 and 788 arcsec, respectively. A plan-view cathodoluminescence (CL) mapping image showed high luminescence intensity on the SiO2 masks. DOI: 10.7567/JJAP.52.08JC04 High Internal Quantum Efficiency Blue-Green Light-Emitting Diode with Small Efficiency Droop Fabricated on Low Dislocation Density GaN Substrate 査読有り Tomotaka Sano, Tomohiro Doi, Shunko Albano Inada, Tomohiko Sugiyama, Yoshio Honda, Hiroshi Amano, and Takashi Yoshino Jpn. J. Appl. Phys. 52 巻 ( 8 ) 頁: 08JK09 2013年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We fabricated blue, blue-green, and green light-emitting diodes (LEDs) of different dislocation densities (DD) and characterized their internal quantum efficiency (IQE). The IQE of the blue LEDs fabricated using GaN substrate exceeded 90 percent, however, when we used a GaN-on-sapphire substrate, IQE was limited to 60 percent. Droop was reduced by use of the GaN substrate. The junction temperature of the GaN-on-sapphire substrate was found to be 200 degreeC although the junction temperature of the GaN substrate was 50 degreeC when a forward current of 100 A/cm2 was driven. A lowering of IQE in green LEDs to 60 percent was observed, even though we used a low-dislocation-density substrate.The junction temperature of blue-green and green LEDs was about 100 degreeC when a forward current of 177 A/cm2 was driven, which indicated that junction temperature is not a major factor for IQE suppression in green LEDs. DOI: 10.7567/JJAP.52.08JK09 Growth Mode and Threading Dislocation Behavior of GaN Films Grown on Patterned Sapphire Substrate with Radial Stripe Pattern 査読有り Koji Okuno, Takahide Oshio, Naoki Shibata, Yoshio Honda, Masahito Yamaguchi, and Hiroshi Amano Jpn. J. Appl. Phys. 52 巻 ( 8 ) 頁: 08JB09 2013年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) A sapphire substrate with a grooved stripe pattern along different radial directions was prepared to investigate the effects of stripe direction on the growth mode and threading dislocation (TD) behavior of GaN films. When the stripe direction is oriented parallel to [1010]sapphire, the GaN films have a triangular structure that is formed by the GaN{1011} facets. As the stripe direction rotates from [1010]sapphire, nanosteps with a step height of around 80 nm are formed on the GaN{1011} facets and then the coalescence of GaN on the ridges and grooves advances. GaN films with a smooth surface and a TD density as low as 2.0×108 cm-2 were achieved when the stripe direction was rotated 3° from [1010]sapphire. Our result indicates that the surface roughness and TD density of GaN films can be controlled by precisely adjusting the angle of the stripe direction from [1010]sapphire. DOI: 10.7567/JJAP.52.08JB09 Thick InGaN Growth by Metal Organic Vapor Phase Epitaxy with Sputtered InGaN Buffer Layer 査読有り Toshiya Ohata, Yoshio Honda, Masahito Yamaguchi, and Hiroshi Amano Jpn. J. Appl. Phys. 52 巻 ( 8 ) 頁: 08JB11 2013年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) A thick InGaN film was grown on a sapphire substrate by metal organic vapor phase epitaxy using a thin buffer layer of sputter-deposited InGaN. A thick film of highly luminescent In0.2Ga0.8N can be successfully grown at a rate as high as 2 µm/h. The crystal quality of InGaN grown on the sputter-deposited InGaN buffer layer was better than that of InGaN grown directly on the sapphire substrate. The sample showed n-type conduction with a carrier concentration and mobility of 5×1018 cm-3 and 3 cm2/(V·s), respectively. DOI: 10.7567/JJAP.52.08JB11 Combination of ITO and SiO2/AlN Dielectric Multilayer Reflective Electrodes for UV-Emitting Diodes 査読有り Tsubasa Nakashima, Kenichiro Takeda, Hiroshi Shinzato, Motoaki Iwaya, Satoshi Kamiyama, Tetsuya Takeuchi, Isamu Akasaki, and Hiroshi Amano Jpn. J. Appl. Phys. 52 巻 ( 8 ) 頁: 08JG07 2013年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We have investigated novel reflective electrodes by combining an ITO layer and a SiO2/AlN dielectric multilayer (DM) for UV-light-emitting diodes (LEDs). The reflectance of 10 pairs of SiO2/AlN DM reached 98.5 percent at 350 nm. As a result, the ITO/DM electrodes simultaneously satisfied the requirements of high reflectivity in the UV region, good contact characteristics, and current spreading. The light output power of the UV LED with an ITO/DM electrode is 1.2 and 1.6 times higher than those of LEDs with ITO/Al and Ni/Au electrodes, respectively. DOI: 10.7567/JJAP.52.08JG07 GaN Nanowires Grown on a Graphite Substrate by Radio Frequency Molecular Beam Epitaxy 査読有り Shinta Nakagawa, Takuya Tabata, Yoshio Honda, Masahito Yamaguchi, and Hiroshi Amano Jpn. J. Appl. Phys. 52 巻 ( 8 ) 頁: 08JE07 2013年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Self-assembled GaN and InGaN nanowires (NWs) were directly grown on a highly oriented pyrolytic graphite (HOPG) substrate by radio frequency molecular beam epitaxy (RF-MBE). The GaN NWs grown on HOPG had a shorter length and larger diameter than those grown conventionally on a Si(111) substrate based on the analysis of scanning electron microscopy (SEM) images. They were also found to have good crystalline qualities with few stacking faults, as determined by scanning transmission electron microscopy (STEM) analysis. Photoluminescence (PL) measurements at room temperature indicated that the luminescence intensity of the GaN NWs on HOPG is stronger than that of NWs grown on a Si(111) substrate; however, the InGaN NWs on both substrates showed similar tendencies with respect to the shift of the luminescence wavelength as a function of the growth temperature. While In incorporation decreased as the growth temperature increased, the uniformity of the InGaN NW arrays improved rapidly. DOI: 10.7567/JJAP.52.08JE07 Concentrating Properties of Nitride-Based Solar Cells Using Different Electrodes 査読有り Mikiko Mori, Shinichiro Kondo, Shota Yamamoto, Tatsuro Nakao1, Motoaki Iwaya, Tetsuya Takeuchi, Satoshi Kamiyama, Isamu Akasaki, and Hiroshi Amano Jpn. J. Appl. Phys. 52 巻 ( 8 ) 頁: 08JH02 2013年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We investigated the concentration properties of GaInN-based solar cells using different window electrodes. A significant difference was observed between the concentrating properties of the window electrode structures. It was clearly found that indium tin oxide (ITO) is suitable as an electrode. The short-circuit current density, open-circuit voltage, fill factor, and energy conversion efficiency of nitride-based solar cells fabricated using an ITO electrode were 7.1×102 mA/cm2, 2.2 V, 79%, and 4.0%, respectively, under an air mass filter of 1.5G at 300 suns and at room temperature. DOI: 10.7567/JJAP.52.08JH02 Emission Wavelength Dependence of Internal Quantum Efficiency in InGaN Nanowires 査読有り Hideaki Murotani, Hiroya Andoh, Takehiko Tsukamoto, Toko Sugiura, Yoichi Yamada, Takuya Tabata, Yoshio Honda, Masatoshi Yamaguchi, and Hiroshi Amano Jpn. J. Appl. Phys. 52 巻 ( 8 ) 頁: 08JE10 2013年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) The internal quantum efficiency (IQE) of InGaN nanowires with different emission wavelength of 485, 515, 555, and 580 nm has been studied by means of photoluminescence (PL) spectroscopy. It was found from the analysis of IQE as a function of excitation power density that the IQE was unchanged at about 100% under weak excitation conditions at low temperature. This indicated that the effects of nonradiative recombination processes were negligibly small at low temperature. Moreover, the IQE increased from 5 to 12% with increasing emission wavelength from 485 to 580 nm. Since the clear correlation between the IQE and the PL blue shift due to band filling effects of localized states was observed, the increase in the IQE reflected the increase in the effect of exciton localization with increasing indium composition. DOI: 10.7567/JJAP.52.08JE10 Luminescence of Acceptors in Mg-Doped GaN 査読有り Bo Monemar, Sergey Khromov, Galia Pozina, Plamen Paskov, Peder Bergman, Carl Hemmingsson, Lars Hultman, Hiroshi Amano, Vitaliy Avrutin, Xing Li, and Hadis Morkoç Jpn. J. Appl. Phys. 52 巻 ( 8 ) 頁: 08JJ03 2013年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) It is concluded that the typical PL peaks at 3.466 eV (ABE1)and the broader 3.27 eV DAP PL are the expected standard PL signatures of the substitutional Mg acceptor. Additional broader peaks at 3.455 eV (ABE2) and 3.1 eV are suggested to be related to the same acceptors perturbed by nearby basal plane stacking faults. The low temperature metastability of PL spectra is assigned to a nonradiative metastable deep level. DOI: 10.7567/JJAP.52.08JJ03 Analysis of Broken Symmetry in Convergent-Beam Electron Diffraction along <11-20 > and <1-100 > Zone-Axes of AlN for Polarity Determination 査読有り Masataka Imura, Ujjal Gautam, Kiyomi Nakajima, Yasuo Koide, Hiroshi Amano, and Kenji Tsuda Jpn. J. Appl. Phys. 52 巻 ( 8 ) 頁: 08JE15 2013年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) To accurately and easily determine the polarity of AlN using transmission electron microscopy, we compare the convergent-beam electron diffraction (CBED) patterns along the widely used <1120 > and <1100 > zone-axes. For the <1120 > zone-axis, the diffraction disk of g= 0002 differs from that of g= 0002, while for <1100 >, the diffraction disks of g= 0002 and 0002 are similar. The preferential clarity of these two disks is explained using Bloch-wave dynamical theory. To further support the explanation, we compare the results of GaN case. On the basis of our analysis, we conclude that the CBED patterns of the <1120 > zone-axis are more useful for accurately determining AlN polarity compared to the CBED patterns along the <1100 > zone-axis. DOI: 10.7567/JJAP.52.08JE15 Microstructure Analysis of AlGaN on AlN Underlying Layers with Different Threading Dislocation Densities 査読有り Kimiyasu Ide, Yuko Matsubara, Motoaki Iwaya, Satoshi Kamiyama, Tetsuya Takeuchi, Isamu Akasaki, and Hiroshi Amano Jpn. J. Appl. Phys. 52 巻 ( 8 ) 頁: 08JE22 2013年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Using the epitaxial lateral growth technique, we compared the crystallinity and relaxation ratio of 3-µm- and 200-nm-thick Al0.5Ga0.5N on an AlN template and AlN grown by epitaxial lateral overgrowth (ELO-AlN), both of which were grown on a sapphire substrate. Although the relaxation ratios of 3-µm-thick Al0.5Ga0.5N were almost the same, the misfit dislocation density at the interface and the density of threading dislocations reaching the surface of Al0.5Ga0.5N were significantly different. Also, the increase in the density of newly generated misfit dislocations was found to be highly dependent on the quality of the AlN underlying layer. We also discuss the difference in the initial growth mode of each Al0.5Ga0.5N sample. DOI: 10.7567/JJAP.52.08JE22 Progress and Prospect of the Growth of Wide-Band-Gap Group III Nitrides: Development of the Growth Method for Single-Crystal Bulk GaN 査読有り Hiroshi Amano Japanese journal of applied physics 52 巻 ( 5 ) 頁: 050001-1-050001-10 2013年5月 詳細を見る 担当区分:筆頭著者 記述言語:英語 掲載種別:研究論文(学術雑誌) With the continuously increasing demand for the conservation and generation of energy, bulk substrates of group III nitride semiconductors are highly expected to maximize their potential. In this report, I review the current status of the growth methods for bulk GaN single crystals used for substrates as well as summarize the characteristics of blue light-emitting diodes (LEDs), heterojunction field-effect transistors (HFETs), and photovoltaic cells on GaN substrates. DOI: 10.7567/JJAP.52.050001 AlN/air distributed Bragg reflector by GaN sublimation from microcracks of AlN 査読有り T. Mitsunari, T. Tanikawa, Y. Honda, M. Yamaguchi, H. Amano Journal of Crystal Growth 370 巻 ( 1 ) 頁: 16-21 2013年5月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) The GaN/AlN multilayer structure was grown on a stripe-patterned and dot-patterned Si substrate, and subsequently annealed at 1200 °C in H2 and NH3 atmosphere. We achieved an AlN/air structure by the decomposition of GaN from the microcracks of AlN. Partially crack-free AlN layers were observed over a 5×5 μm area in the c-plane of AlN/air DBRs. DOI: 10.1016/j.jcrysgro.2012.09.062 Structural evolution of AlN buffer and crystal quality of GaN films on a- and c-sapphire grown by metalorganic vapor phase epitaxy 査読有り Okuno, Koji; Oshio, Takahide; Shibata, Naoki; Honda, Yoshio; Yamaguchi, Masahito; Tanaka, Shigeyasu; Amano, Hiroshi Physica Status Solidi C 10 巻 ( 3 ) 頁: 369-372 2013年3月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 0.1002/pssc.201200587 Effects of low energy e-beam irradiation on cathodoluminescence from GaN 査読有り Suihkonen, S.; Nykaenen, H.; Tanikawa, T.; Yamaguchi, M.; Honda, Y.; Amano, H. Physica Status Solidi A 210 巻 ( 2 ) 頁: 383-385 2013年2月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1002/pssa.201228457 Development of High-Density Nitrogen Radical Source for Low Mosaicity and High Rate Growth of InGaN Films in Molecular Beam Epitaxy 査読有り Chen, S ; Kawai, Y ; Kondo, H ; Ishikawa, K ; Takeda, K ; Kano, H ; Sekine, M ; Amano, H Hori, M Japanese Journal of Applied Physics 52 巻 ( 2 ) 頁: 021001-021006 2013年2月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) A high-density radical source (HDRS) was developed by optimizing the antenna structure and introducing an external magnetic field to plasma. Nitrogen radical generation by the HDRS at a density of 2.3 ×1012 atoms cm-3, which was one order higher than that for the conventional radical source (CRS), was achieved. The HDRS- and CRS-assisted InGaN growth in molecular beam epitaxy (MBE) was carried out. For the HDRS case, a diffraction peak in the X-ray rocking curve of the grown InGaN films showed a narrower peak, which width below 600 arcsec even with a high growth rate of 1.4 µm/h for InGaN. MBE with the assistance of HDRS has a great potential in the growth of nitride films with a lower mosaicity and a higher growth rate. DOI: 10.7567/JJAP.52.021001 Surface potential effect on excitons in AlGaN/GaN quantum well structures 査読有り Pozina, G.; Hemmingsson, C.; Amano, H.; Monemar, B. Applied Physics Letters 102 巻 ( 8 ) 頁: 082110/1-082110/4 2013年2月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1063/1.4793568 Individual roles of atoms and ions during hydrogen plasma passivation of surface defects on GaN created by plasma etching 査読有り Chen, Shang; Ishikawa, Kenji; Lu, Yi; Kometani, Ryosuke; Kondo, Hiroki; Tokuda, Yutaka; Egawa, Takashi; Amano, Hiiroshi; Sekine, Amano; Hori, Masaru Japanese Journal of Applied Physics 51 巻 ( 11 ) 頁: 111002/1-11102/5 2012年11月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) In the recovery of photoluminescence intensities for band-edge emissions at around 3.47 eV in the case of gallium nitride (GaN), we have studied the individual roles of hydrogen atoms (H) and hydrogen ions (H-n(+)). Surface defects such as nitrogen vacancies created by plasma etching were passivated by H termination. By utilizing hydrogen plasmas, we clarified the recovery efficiency by optical and stoichiometrical improvements with respect to the balance between the fluxes of H and H-n(+). By deflecting H-n(+) by applying an electric field, the efficiency was improved using an identical H dosage, since the simultaneous irradiation of the energetic H-n(+) promoted the desorption of the formed passivated Ga-H bonds. DOI: 10.1143/JJAP.51.111002 Correlation between device performance and defects in GaInN-based solar cells 査読有り Mori, Mikiko; Kondo, Shinichiro; Yamamoto, Shota; Nakao, Tatsuro; Fujii, Takahiro; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi Applied Physics Express 5 巻 ( 8 ) 頁: 082301/1-082301/3 2012年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We investigated the correlation between the device performance and defects, such as V-shaped pits and threading dislocations, in GaInN-based solar cells. To realize high-performance GaInN-based solar cells with a high open-circuit voltage and fill factor, it is essential to realize a low pit density of less than 10(7) cm(-2). In this study, we were unable to observe clear evidence of any effect of the threading dislocation density in the GaN underlying layer. DOI: 10.1143/APEX.5.082301 MOVPE growth of nonpolar a-plane GaN with low oxygen contamination and specular surface on a freestanding GaN substrate 査読有り Yasuhiro Isobe, Hiromichi Ikki, Tatsuyuki Sakakibara, Motoaki Iwaya, Tetsuya Takeuchi, Satoshi Kamiyama, Isamu Akasaki,Takayuki Sugiyama, Hiroshi Amano, Mamoru Imade, Yusuke Mori Journal of Crystal Growth 351 巻 ( 1 ) 頁: 126-130 2012年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We investigated unintentionally doped nonpolar a- and m-plane GaN layers grown by metalorganic vapor phase epitaxy under several sets of conditions on freestanding a- and m-plane GaN substrates. Oxygen contamination in a-plane GaN is greatly reduced by increasing the V/III ratio during growth. As a result, a high-resistivity GaN buffer layer for an AlGaN/GaN heterostructure field-effect transistor was realized. In-situ void formation technique using an AlN shell structure grown on GaN stripes on Si(111) and c-plane sapphire substrates 査読有り Mitsunari, Tadashi; Tanikawa, Tomoyuki; Honda, Yoshio; Yamaguchi, Masahito; Amano, Hiroshi Physca Status Solidi c 9 巻 ( 3-4 ) 頁: 480-483 2012年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We proposed an in-situ void formation technique using high-temp. AlN growth on GaN stripes in order to reduce residual stress. Microcracks were obsd. during the growth of AlN; the GaN stripes then sublimated from the microcracks while keeping the AlN shell, resulting in void formation in the AlN shell structure. After GaN regrowth on this AlN shell structure, we successfully coalesced the GaN stripes to form a smooth, thick GaN layer having voids at the GaN/substrate interface. Raman spectroscopy confirmed that the residual tensile stress was decreased. The thermal stress decreased owing to the sepn. between the GaN layer and a foreign substrate. DOI: 10.1002/pssc.201100502 Small current collapse in AlGaN/GaN HFETs on a-plane GaN self-standing substrate 査読有り T. Sugiyama, Y. Honda, M. Yamaguchi, H. Amano, Y. Isobe, M. Iwaya, T. Takeuchi, S. Kamiyama, I. Akasaki, M. Imade, Y. Kitaoka, Y. Mori Physica Status Solidi c 9 巻 ( 3-4 ) 頁: 875-878 2012年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We measured drain bias stress effects and current collapse in AlGaN/ GaN heterostructure field-effect transistors (HFETs) on a-plane and c-plane GaN substrates. An a-plane AlGaN/GaN HFET (a-HFET) shows small current collapse with a threshold voltage (Vth = -1.8 V). On the other hand, a c-plane HFET (c-HFET) with the same barrier thickness (20 nm) shows a small current collapse, although Vth was neg. large (Vth = -4 V). Current collapse in a-HFET was not large compared with that in conventional c-HFET on GaN. A c-HFET on sapphire was also measured. The current collapses in HFETs on sapphire were larger than that in HFETs on a GaN substrate. The current collapses in the thin-barrier c-HFET (Vth = -1.8 V) were particularly large. Therefore, an a-plane device is promising for a small or pos. Vth with small current collapse. DOI: 10.1002/pssc.201100397 Laser lift-off of AlN/sapphire for UV light-emitting diodes 査読有り Aoshima, Hiroki; Takeda, Kenichiro; Takehara, Kosuke; Ito, Shun; Mori, Mikiko; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi Physica Status Solidi C 9 巻 ( 3-4 ) 頁: 753-756 2012年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We report on laser lift-off (LLO) of AlN/sapphire for UV light-emitting diodes (LEDs). Underfill between chip and submount is a key factor for the successful LLO of AlN/sapphire. We fabricated thin-film-flip-chip UV LEDs with a peak wavelength of 343 nm using the LLO. Moreover surface texturing was carried out on the exfoliated AlN surface. The light output power from the UV LED after the LLO and the surface texture at exfoliated surface is 1.7 times higher than that before the LLO at 20 mA. DOI: 10.1002/pssc.201100491 Growth of InGaN nanowires on a (111)Si substrate by RF-MBE 査読有り Tabata, Takuya; Paek, Jihyun; Honda, Yoshio; Yamaguchi, Masahito; Amano, Hiroshi Physica Status Solidi c 9 巻 ( 3-4 ) 頁: 646-649 2012年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We have grown InGaN nanowires (NWs) on a (111)Si substrate directly by radio-frequency plasma-assisted mol. beam epitaxy (RF-MBE), and investigated their In compositional distribution by energy dispersive x-ray spectroscopy (EDX). The In compn. line profiles of InGaN NWs measured by EDX are different at each position in the InGaN NWs, and In is most easily incorporated into the top of NWs. The In compn. at the top of the NWs depends on the growth temp. and the In flux ratio. However, the In compns. at other positions is not dependent on these factors. Thus, these results might be due to the limited diffusion of In atoms from the top of the NWs towards the NWs/Si interface. DOI: 10.1002/pssc.201100446 Fabrication of AlInN/AlN/GaInN/GaN heterostructure field-effect transistors 査読有り Kazuya Ikeda, Yasuhiro Isobe, Hiromichi Ikki, Tatsuyuki Sakakibara, Motoaki Iwaya, Tetsuya Takeuchi, Satoshi Kamiyama, Isamu Akasaki, Hiroshi Amano Physica Status Solidi c 9 巻 ( 3-4 ) 頁: 942-944 2012年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We report on the electrical properties of AlInN/GaInNheterostructures fabricated with InN molar fractions of 0 to 0.6 in the GaInN layer. High-density two-dimensional electron gases are formed near the interfaces of AlInN/AlN/GaInN at InN molar fractions of 0.3 and 0.6.The Al0.82In0.18N/AlN/Ga0.4In0.6N/GaN heterostructurefield-effect transistors exhibited static characteristics.The maximum drain-source current reached a value of0.26 A/mm. DOI: 10.1002/pssc.201100492 High carrier concentration in high Al-composition AlGaN-channel HEMTs 査読有り Hashimoto, Shin; Akita, Katsushi; Yamamoto, Yoshiyuki; Ueno, Masaki; Nakamura, Takao; Yafune, Norimasa; Sakuno, Keiichi; Tokuda, Hirokuni; Kuzuhara, Masaaki; Takeda, Kenichiro; Iwaya, Motoaki; Amano, Hiroshi 9 巻 ( 2 ) 頁: 373-376 2012年6月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) High Al-compn. (Al = 51%) and low Al-compn. (Al = 20%) AlGaN-channel high-electron-mobility transistors (HEMTs) on AlN layers with very high carrier concn. were demonstrated. In two types of HEMTs, 2-dimensional electron gases (2DEG) were clearly obsd. and peak carrier concn. and sheet carrier concn. were approx. 1020 cm-3 and higher than 2 × 1013 cm-2, resp. From the X-ray diffraction (XRD) measurements, it was obsd. that the AlGaN channel layers on the AlN layers were partially relaxed and the degree of relaxation decreased with increasing Al-compn. of AlGaN channel layers. Therefore the misfit dislocations in the high Al-compn. HEMTs were considered to be lower than those in the low Al-compn. HEMTs. Furthermore, it was revealed that very high Al-compn. of AlGaN barrier layers can be grown coherently on the AlGaN channel layers in consequence of the partly relaxation of the AlGaN channel layers, which of lattice consts. of a-axis were smaller than that of fully relaxed AlGaN channel layers. Therefore very high carrier concn. of 2DEG can be obtained in spite of the high Al-compn. of AlGaN channel layers. We considered that this high carrier concn. of 2DEG was necessary to demonstrate high Al-compn. AlGaN-channel HEMTs. DOI: 10.1002/pssc.201100289 窒化物ワイドギャップ半導体の現状と展望 ―バルクGaN単結晶成長技術開発の観点から― 査読有り 天野 浩 応用物理 81 巻 ( 6 ) 頁: 455-463 2012年6月 詳細を見る 担当区分:筆頭著者 記述言語:日本語 掲載種別:研究論文(学術雑誌) GaNのバルク成長の歴史と展望を概説した。 Crack-Free AlN/GaN Distributed Bragg Reflectors on AlN Templates 査読有り Kouta Yagi, Mitsuru Kaga, Kouji Yamashita, Kenichirou Takeda, Motoaki Iwaya, Tetsuya Takeuchi, Satoshi Kamiyama, Hiroshi Amano, and Isamu Akasaki Japanese Journal of Applied Physics 51 巻 頁: 051001 2012年5月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We have demonstrated crack-free 30-pair-AlN/GaN distributed Bragg reflectors (DBRs) grown on AlN templates for the first time. A reasonably high reflectivity of 97.5% was obtained. X-ray diffraction measurements revealed that the AlN templates cause compressive stress in DBRs. At the same time, the AlN/GaN DBRs were found to relax to average AlGaN alloys with AlN mole fractions determined by the thickness ratio of the AlN layer to one pair of AlN and GaN in DBRs regardless of the underlying template, AlN or GaN. DOI: 10.1143/JJAP.51.051001 Growth of GaN and AlGaN on (100) beta-Ga2O3 substrates 査読有り Shun Ito, Kenichiro Takeda, Kengo Nagata, Hiroki Aoshima, Kosuke Takehara, Motoaki Iwaya, Tetsuya Takeuchi, Satoshi Kamiyama, Isamu Akasaki, Hiroshi Amano 9 巻 ( 3-4 ) 頁: 519-522 2012年5月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) The crystalline quality of GaN and Al0.08Ga0.92N epitaxial layers on (100) β-Ga2O3 substrates was significantly improved by the facet-controlled growth method. The facets were controlled by changing the nitrogen ambient thermal annealing temperature. We demonstrated the highcrystalline-quality GaN and Al0.08Ga0.92N on β-Ga2O3 substrates, which were comparable to GaN and AlGaN on sapphire substrates using low-temperature buffer layers.This method is useful for the fabrication of verticaltype ultraviolet (UV) light-emitting diodes (LEDs) on β-Ga2O3 substrates. DOI: 10.1002/pssc.201100499 Properties of nitride-based photovoltaic cells under concentrated light illumination 査読有り Shota Yamamoto, Mikiko Mori, Yosuke Kuwahara, Takahiro Fujii, Tatsuo Nakao, Shinichiro Kondo, Motoaki Iwaya, Tetsuya Takeuchi, Satoshi Kamiyama, Isamu Akasaki, Hiroshi Amano Physica Status Solidi Rapid Research Letter 6 巻 ( 4 ) 頁: 145-147 2012年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We investigated the properties of nitride-based solar cells under concentrated light illumination from 1 to 200 suns. The conversion efficiency of our solar cells increased with increasing concentration up to 200 suns. The short-circuit cur- rent density, open-circuit voltage, fill factor, and conversion efficiency were 510 mA/cm2, 1.9 V, 70%, and 3.4%, respectively, under an air mass filter of 1.5G at 200 suns and room temperature. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) DOI: DOI: 10.1002/pssr.201206038 Development of AlN/diamond heterojunction field effect transistors 査読有り Masataka Imura, Ryoma Hayakawa, Hirotaka Ohsato, Eiichiro Watanabe, Daiju Tsuya, Takahiro Nagata, Meiyong Liao, Yasuo Koide, Jun-ichi Yamamoto, Kazuhito Ban, Motoaki Iwaya, Hiroshi Amano Diamond and Related Materials 24 巻 頁: 206-209 2012年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) AlN/diamond heterojunction field effect transistors with p-channel and normally-on depletion mode are developed, and the device performance is improved by reducing the contact resistances at source and drain contacts reported previously. The heterojunction structure is constructed from a c-axis-oriented AlN epilayer grown on oxygen-terminated (111) diamond substrate by metal-organic vapor phase epitaxy at temperatures as high as 1250 °C. Thermal treatment in the mixed hydrogen (H2) and ammonia atmosphere just before AlN growth improves the AlN adhesion to diamond surface. In addition, this treatment simultaneously produces a much larger surface hole-carrier density than that obtained by conventional H2-plasma treatment. X-ray photoelectron spectroscopy reveals the existence of carbon-nitrogen bonds at the diamond surface, and these may be responsible for such a large hole density. These results are promising in relation to new opportunities for developing diamond-based power electronic devices. Indium-Tin Oxide/Al eflective Electrodes for Ultraviolet Light-Emitting Diodes 査読有り Kosuke Takehara, Kenichiro Takeda, Shun Ito, Hiroki Aoshima, Motoaki Iwaya, Tetsuya Takeuchi, Satoshi Kamiyama, Isamu Akasaki, and Hiroshi Amano Japanese Journal of Applied Physics 51 巻 頁: 042101 2012年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1143/JJAP.51.042101 Indium-Tin oxide/Al reflective electrodes for ultraviolet light-emitting diodes 査読有り Takehara, Kosuke; Takeda, Kenichiro; Ito, Shun; Aoshima, Hiroki; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi 51 巻 ( 4 ) 頁: 042101/1-042101/4 2012年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We investigated indium-tin oxide (ITO)/Al reflective electrodes for improving the light extraction efficiency of UV light-emitting diodes (LEDs). The ITO layer showed high transparency in the UV region upon optimization of the thickness and annealing temperature. As a result, the ITO/Al electrode exhibited both high reflectivity in the UV region and good contact characteristics simultaneously. Using this electrode, we succeeded in improving the light output power of a 350 nm UV-A LED. DOI: 10.1143/JJAP.51.042101 Strain relaxation in thick (1-101) InGaN grown on GaN/Si substrate 査読有り Tomoyuki Tanikawa, Yoshio Honda, Masahito Yamaguchi, Hiroshi Amano, Nobuhiko Sawaki Physica Status Solidi b 249 巻 頁: 468-471 2012年3月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: DOI: 10.1002/pssb.201100445 Enhancement of two-dimensional electron gases in AlGaN-channel high-electron-mobility transistors with AlN barrier layers 査読有り Hashimoto Shin; Akita Katsushi; Yamamoto Yoshiyuki, HIroshi Amano Physica Status Solidi a 209 巻 頁: 501-504 2012年3月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: DOI: 10.1002/pssa.201100379 Improvement of Light Extraction Efficiency for AlGaN-Based Deep Ultraviolet Light-Emitting Diodes 査読有り Tetsuhiko Inazu, Shinya Fukahori, Cyril Pernot, Myung Hee Kim, Takehiko Fujita, Yosuke Nagasawa, Akira Hirano, Masamichi Ippommatsu, Motoaki Iwaya, Tetsuya Takeuchi, Satoshi Kamiyama, Masahito Yamaguchi, Yoshio Honda, Hiroshi Amano, and Isamu Akasaki Japanese Journal of Applied Physics 50 巻 頁: 122101 2011年12月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) AlGaN-based deep ultraviolet light-emitting diodes (LEDs) with aluminum reflective electrodes deposited to cover both p- and n-mesh contact electrodes have been fabricated. A 1.55-fold increase in light extraction efficiency has been demonstrated. Despite their reduced contact area, the LEDs exhibited only a slight increase in forward voltage of 0.45 V at 20 mA. Also, their 50% lifetime was estimated to be about 10,000 h at 20 mA DC at room temperature by extrapolation. Owing to the reflective electrodes, a 288 nm LED with external quantum efficiency as high as 5.4% was achieved. The light output power was 4.6 mW at 20 mA. DOI: 10.1143/JJAP.50.122101 Dependence of Resonance Energy Transfer on Exciton Dimensionality 査読有り Jan Junis Rindermann, Galia Pozina, Bo Monemar, Lars Hultman, Hiroshi Amano, and Pavlos G. Lagoudakis Physical Review Letters 107 巻 頁: 236805 2011年11月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We investigate the dependence of resonance energy transfer from Wannier-Mott excitons to an organic overlayer on exciton dimensionality. We exploit the excitonic potential disorder in a single quantum well to tune the balance between localized and free excitons by scaling the Boltzmann distribution of excitons through temperature. Theoretical calculations predict the experimentally observed temperature dependence of resonance energy transfer and allow us to quantify the contribution of localized and free excitons. We show that free excitons can undergo resonance energy transfer with an order of magnitude higher rate compared to localized excitons, emphasizing the potential of hybrid optoelectronic devices utilizing resonance energy transfer as a means to overcome charge transfer related limitations. Fabrication of Nonpolar a-Plane Nitride-Based Solar Cell on r-Plane Sapphire Substrate 査読有り Applied Physics Express 4 巻 頁: 101001 2011年10月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) サファイアr面基板上に成長した窒化物太陽光発電素子に関する初めての論文。 DOI: 10.1143/APEX.4.101001 AlGaN-Based Deep Ultraviolet Light-Emitting Diodes Fabricated on Patterned Sapphire Substrates 査読有り Myunghee Kim, Takehiko Fujita, Shinya Fukahori, Tetsuhiko Inazu, Cyril Pernot, Yosuke Nagasawa, Akira Hirano, Masamichi Ippommatsu, Motoaki Iwaya, Tetsuya Takeuchi, Satoshi Kamiyama, Masahito Yamaguchi, Yoshio Honda, Hiroshi Amano, and Isamu Akasaki Applie Physics Express 4 巻 頁: 092102 2011年9月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1143/APEX.4.092102 AlGaN/GaN Heterostructure Field-Effect Transistors on Fe-Doped GaN Substrates with High Breakdown Voltage 査読有り Yoshinori Oshimura, Takayuki Sugiyama, Kenichiro Takeda, Motoaki Iwaya, Tetsuya Takeuchi, Satoshi Kamiyama, Isamu Akasaki and Hiroshi Amano Japanese Journal of Applied Physics 50 巻 頁: 084102 2011年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) lGaN/GaN heterostructure field-effect transistors (HFETs) were fabricated by metalorganic vapor phase epitaxy (MOPVE) on c-plane Fe-doped GaN (GaN:Fe) substrates with different growth conditions of GaN buffer layers. The GaN buffer layers were grown at a V/III ratio of 272 at 300 Torr to realize highly resistive GaN buffer layers with automatic carbon doping. HFETs with carbon-doped GaN buffer layers showed the best characteristics among all the samples in this study. The carbon concentration was 5×1016 cm-3. In the sample with a gate-drain length of 50 µm, the off-state breakdown voltage was 2 kV or higher and the on-resistance was 18.5 mΩ·cm2. We found that the carbon-doped GaN buffer layers are necessary for high breakdown voltages even using semi-insulating GaN:Fe substrates. Luminescence related to high density of Mg-induced stacking faults in homoepitaxially grown GaN 査読有り S. Khromov, C. G. Hemmingsson, H. Amano, B. Monemar, L. Hultman, and G. Pozina Pysical Review B84 巻 頁: 075324 2011年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) DOI: 10.1103/PhysRevB.84.075324 Reduction in threshold current density of 355 nm UV laser diodes 査読有り Nagata, Kengo; Takeda, Kenichiro; Nonaka, Kentaro; Ichikawa, Tomoki; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi; Yoshida, Harumasa; et al Physica Status Solidi C 8 巻 ( 5 ) 頁: 1564-1568 2011年8月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We have investigated the characteristics of 355 nm UV laser diodes. Two laser diode structures were prepd. on a grooved AlGaN template as well as on a flat AlGaN template. The threading dislocation densities on the grooved and flat AlGaN were 2.5 × 108 cm-2 and 6.5 × 109 cm-2, resp. The threshold c.d. of the laser diode on the grooved AlGaN was 6 kA/cm2, while no lasing was obsd. from the laser diode on the flat AlGaN. We also estd. the internal quantum efficiency as well as the injection efficiency in the UV laser diode structures by considering internal quantum efficiency of both optical and elec. excitation. At a carrier d. of 1.2 × 1019 cm-3, the internal quantum efficiency of the laser diode structure on the grooved AlGaN was about 50%. This is twice that of the laser diode on the flat AlGaN. At the same time, the internal quantum efficiency estd. from the optical excitation also reached about 50%, even at a carrier d. of 3 × 1018 cm-3. This implies that the injection efficiency in our UV laser diode structure was only 25%. Improving the injection efficiency should be effective for significantly reducing the threshold c.d. GaInN-based solar cells using GaInN/GaInN superlattices 査読有り Fujii, Takahiro; Kuwahara, Yousuke; Iida, Daisuke; Fujiyama, Yasuhara; Morita, Yoshiki; Sugiyama, Toru; Isobe, Yasuhiro; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; et al Physica Status Solidi C 8 巻 ( 7-8 ) 頁: 2463-2465 2011年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We report on the fabrication of GaInN-based solar cells using GaInN/GaInN superlattices as active layers and also as underlying layers beneath the active layers. We obtained pit-free surfaces, even with a high InN molar fraction, using the superlattices. As a result, the max. external and internal quantum efficiencies reached 60%, and 88%, resp. The open-circuit voltage of the soalr cells was 1.77 V, the short-circuit c.d. was 3.08 mA/cm2, and the fill factor was 70.3%. A conversion efficiency of 2.46% was achieved at room temp. under simulared 1.5 sun × AM1.5G illumination using a solar simulator. Injection efficiency in AlGaN-based UV laser diodes 査読有り Nagata, Kengo; Takeda, Kenichiro; Oshimura, Yoshinori; Takehara, Kosuke; Aoshima, Hiroki; Ito, Shun; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; et al Physica Status Solidi C 8 巻 ( 7-8 ) 頁: 2384-2386 2011年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We evaluated AlGaN-based 355 nm UV laser diodes prepd. under two different Mg activation conditions. The annealing processes for Mg activation in p-layers were carried out under N2 or O2 ambient to investigate the effect of the ambient gas on the laser characteristics. The threshold current densities and operating voltages of the UV laser diodes were improved by annealing under O2 compared with those under N2. We then estd. the injection efficiencies of the laser diode structures by considering the internal quantum efficiencies of optical excitation and elec. excitation. The internal quantum efficiency of the elec. excited spontaneous emission from the laser structure annealed under O2 reached 50% at a carrier d. of 7.0 × 1018 cm-3, while the structure annealed under N2 required a 1.8-fold higher carrier d. of 1.2 × 1019 cm-3 to reach the same internal quantum efficiency. In addn., the internal quantum efficiency estd. from optical excitation reached 50% even at a carrier d. of 3.0 × 1018 cm-3. This implies that the injection efficiencies in the UV laser diode structures annealed under N2 and O2 were 25% and 45%, resp. Mg activation by O2 annealing is effective for increasing the injection efficiency. Low leakage current in AlGaN/GaN HFETs with preflow of Mg source before growth of u-GaN buffer layer 査読有り Oshimura, Yoshinori; Sugiyama, Takayuki; Takeda, Kenichiro; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi Physica Status Solidi A 208 巻 ( 7 ) 頁: 1607-1610 2011年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) AlGaN/GaN heterostructure field-effect transistors were grown by metalorg. vapor phase epitaxy on Fe-doped GaN substrates with a preflow of the Mg source. We realized a low drain leakage current, 1.05 μA/mm, at VDS = 20 V and VGS = -5 V with LGD = 3 μm. This leakage current was one order of magnitude lower than that obtained without a preflow of the Mg source. The breakdown voltage was over 250 V with LGD = 10 μm. The on resistance was estd. to be 3.6 mΩ cm2. No significant redistribution or memory effect of Mg was obsd. by secondary ion mass spectroscopy measurement. Optical properties of (1-101) InGaN/GaN MQW stripe laser structure on Si substrate 査読有り Murase, Tasuku; Tanikawa, Tomoyuki; Honda, Yoshio; Yamaguchi, Masahito; Amano, Hiroshi Physica Status Solidi C 8 巻 ( 7-8 ) 頁: 2160-2162 2011年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) A smooth laser structure on (1-101) GaN microstripes was successfully fabricated on a patterned (100) 8°-off Si substrate. The sample has a high internal quantum efficiency (IQE) compared with blue LEDs on a sapphire substrate. The high-d. excitation PL spectrum obsd. from the cross section of the sample shows marked narrowing, and the integral PL intensity also shows a steep increase. These results indicate the onset of stimulated emission from an InGaN-based multi quantum well (MQW) active layer on (1-101) GaN (100) Si. To the best of our knowledge, this is the first report of the observation of a stimulated emission from a (1-101) MQW on a Si substrate. We succeeded in fabricating and verifying the high-quality laser structure on semipolar (1-101) GaN on a Si substrate. Optimization of initial MOVPE growth of non-polar m- and a-plane GAN on Na flux grown LPE-GaN substrates 査読有り Isobe, Yasuhiro; Iida, Daisuke; Sakakibara, Tatsuyuki; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi; Imade, Mamoru; Kitaoka, Yasuo; et al Physica Status Solidi C 8 巻 ( 7-8 ) 頁: 2095-2097 2011年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We optimized the initial GaN growths of nonpolar m- and a-plane GaN grown on liq. phase epitaxy (LPE-) GaN substrates. Such nonpolar LPE-GaN substrates were produced by cutting slices from c-plane LPE-GaN bulk single crystals grown by the Na-flux method. We investigated the qualities of epitaxially grown GaN layers on the LPE-GaN substrates, with different polishing methods, which are chem. mech. polishing and plasma dry etch polishing. We found that the cryst. quality of epitaxial GaN on m-plane GaN is very sensitive to the surface polishing even the minute unevenness in GaN substrate. Our expts. also indicated that a low initial growth rate was necessary to obtain high-cryst.-quality epitaxial m-plane GaN. In contrast, high-cryst.-quality a-plane GaN was obtained even with a high initial growth rate, indicating that the cryst. quality of a-plane GaN is not sensitive to surface roughness. Selective MOVPE growth of InGaN/GaN MQW on microfacet GaN stripes 査読有り Tanikawa, Tomoyuki; Murase, Tasuku; Honda, Yoshio; Yamaguchi, Masahito; Amano, Hiroshi Physica Status Solidi C 8 巻 ( 7-8 ) 頁: 2038-2040 2011年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We demonstrated the effects of growth conditions such as growth pressure and growth temp. during the selective growth of InGaN/GaN multiple quantum wells (MQWs) on semipolar GaN microstripes on Si substrates. Grown layers exhibited the ridge growth, which indicates the thickness fluctuation, owing to the source supply from the apexes of the GaN microstructure. Ridge growth was suppressed by increasing growth pressure and decreasing growth temp. Cathode luminescence (CL) anal. showed uniform luminescence. As a result, high pressure and low temp. are suitable for obtaining uniform heterostructures in the selective growth of InGaN/GaN MQWs on GaN microstripes. Transparent electrode for UV light-emitting-diodes 査読有り Takehara, Kosuke; Takeda, Kenichiro; Nagata, Kengo; Sakurai, Hisashi; Ito, Shun; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi Physica Status Solidi C 8 巻 ( 7-8 ) 頁: 2375-2377 2011年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We have investigated the transparent electrodes using indium tin oxide (ITO) for UV light-emitting diodes (LEDs). The carrier concn. of ITO was increased from 1.1 × 1018 to 1.5 × 1021 cm-3 after annealing under N2 ambient at 600 °C. The fundamental absorption edge was also shifted to a shorter wavelength owing to the increase in carrier concn., through the so-called the Burstein-Moss effect. The annealed ITO forms an ohmic contact with p-GaN with a specific contact resistance of 1.2 × 10-3 Ωcm2. The light output power of a 350 nm LED with the annealed ITO contact is 1.2 times higher than that with a conventional Ni/Au contact. Drain bias stress and memory effects in AlGaN/GaN heterostructure field-effect transistors with p-GaN gate 査読有り Sugiyama, Takayuki; Honda, Yoshio; Yamaguchi, Masahito; Amano, Hiroshi; Oshimura, Yoshinori; Iida, Daisuke; Iwaya, Motoaki; Akasaki, Isamu Physica Status Solidi C 8 巻 ( 7-8 ) 頁: 2424-2426 2011年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We measured the drain bias stress effects in normally off mode AlGaN/GaN (JHFETs) with a p-GaN gate, whose AlGaN barrier was exposed to air by dry etching. A large current collapse and a memory effect decreased the drain current (IDS). IDS of an unpassivated sample became the off leakage level of normally off mode JHFETs at a drain stress bias of 15 V. On the other hand, IDS in SiN-passivated JHFETs decreased at a slow rate upon applying drain stress bias. The decrease in IDS in SiN-passivated JHFETs was almost the same as that in asgrown HFETs. These drain stress and memory effects were perfectly deletable by light exposure, and were rewritable similarly in an EPROM. Achieving high-growth-rate in GaN homoepitaxy using high-density nitrogen radical source 査読有り Kawai, Yohjiro; Chen, Shang; Honda, Yoshio; Yamaguchi, Masahito; Amano, Hiroshi; Kondo, Hiroki; Hirmatsu, Mineo; Kano, Hiroyuki; Yamakawa, Koji; Den, Shoji; et al Physica Status Solidi C 8 巻 ( 7-8 ) 頁: 2089-2091 2011年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) The key issue in GaN growth by radio-frequency plasma-assisted mol. beam epitaxy is the low growth rate compared with that obtained using an ammonia source. To reduce the processing time and to improve the cryst. quality of the epilayer, a high-d. radical source (HDRS) with high stability has been developed. The growth rate of the GaN epilayer was improved using the HDRS rather than a conventional radical source. During the growth, a sharp streak pattern obtained by RHEED was maintained. An atomically smooth surface was confirmed by at. force microscopy observation. AlGaN/GaInN/GaN heterostructure field-effect transistor 査読有り Ikki, Hiromichi; Isobe, Yasuhiro; Iida, Daisuke; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi; Bandoh, Akira; Udagawa, Takashi Physica Status Solidi A 208 巻 ( 7 ) 頁: 1614-1616 2011年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We report on the elec. properties of AlGaN/GaInN heterostructures fabricated with various InN molar fractions from 0 to 0.60 in GaInN on a GaN template. The sheet carrier d. of the AlGaN/GaInN heterostructure monotonically increased with increasing InN molar fraction in GaInN, reaching 5.0 × 1013 cm-2 at an InN molar fraction of 0.60. The Al0.30Ga0.70N/Ga0.40In0.60N heterostructure exhibited static field-effect transistor (FET) characteristics. Development of high efficiency 255-355 nm AlGaN-based light-emitting diodes 査読有り Pernot, Cyril; Fukahori, Shinya; Inazu, Tetsuhiko; Fujita, Takehiko; Kim, Myunghee; Nagasawa, Yosuke; Hirano, Akira; Ippommatsu, Masamichi; Iwaya, Motoaki; Kamiyama, Satoshi, Amano Hiroshi; et al Physica Status Solidi A: 208 巻 ( 7 ) 頁: 1594-1596 2011年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We report on the fabrication and characterization of high efficiency UV light emitting diodes (LEDs) with emission wavelength ranging from 255 to 355 nm. Epi-layers of UV LEDs were grown on AlGaN templates with sapphire substrates. Flip-chip configuration without removing sapphire is used for characterization of the UV LEDs. External quantum efficiencies (EQEs) over 3% were obtained for all the investigated wavelengths with max. value reaching 5.1% for 280 nm LED. Under RT DC operation at a current of 500 mA, output powers of 38, 77, and 64 mW were measured for 257, 280, and 354 nm, resp. By using enhanced light extn. technologies, such as, moth-eye structure on the back side of the sapphire substrate, we expect to improve these values by up to 50%. Nonpolar a-plane AlGaN/GaN heterostructure field-effect transistors grown on freestanding GaN substrate 査読有り Isobe, Yasuhiro; Ikki, Hiromichi; Sakakibara, Tatsuyuki; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Sugiyama, Takayuki; Amano, Hiroshi; Imade, Mamoru; et al Applied Physics Express 4 巻 ( 6 ) 頁: 064102/1-064102/3 2011年6月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We fabricated and characterized nonpolar a-plane AlGaN/GaN heterostructure field-effect transistors (HFETs) grown on an a-plane freestanding GaN substrate. By optimizing the growth conditions, the unintentionally doped oxygen concn. was much reduced in the a-plane GaN buffer layer. As a result, the low leakage current in the buffer layer was realized without doping of deep acceptors, such as Fe and C, by which an impurity-contamination-free channel layer can be successfully grown. Effect of lateral vapor phase diffusion during the selective growth of InGaN/GaN MQW on semipolar and nonpolar GaN stripes 査読有り Tanikawa, Tomoyuki; Honda, Yoshio; Yamaguchi, Masahito; Amano, Hiroshi Physica Status Solidi A 208 巻 ( 5 ) 頁: 1175-1178 2011年5月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We investigated the InGaN/GaN multiple quantum well (MQW) thickness and cathode luminescence (CL) distribution on nonpolar (11-20)GaN, semipolar (11-22)GaN, and (1-101)GaN microstripes grown by selective metal-org. vapor phase epitaxy (MOVPE) on patterned Si substrates. All samples exhibited ridge growth. To clarify the effect of vapor phase diffusion, the two-dimensional diffusion equation was solved. The results were in good agreement with the thickness distribution on the (11-20)GaN stripe when we assumed D/k0 to be 1 μm. However, the results were not in agreement for the semipolar case. On the semipolar face, the surface migration length might be greater, thus increasing the thickness nonuniformity. CL anal. indicated a uniform indium compn. on the (11-20) and (11-22) faces. On the (1-101)GaN stripe, the indium compn. decreased near the (0001) edge. Excess Ga is considered to affect the compositional nonuniformity on the (1-101) facet. Evidence for moving of threading dislocations during the VPE growth in GaN thin layers 査読有り Kuwano, Noriyuki; Miyake, Hideto; Hiramatsu, Kazumasa; Amano, Hiroshi; Akasaki, Isamu Physica Status Solidi C 8 巻 ( 5 ) 頁: 1487-1490. 2011年5月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Cross-sectional transmission electron microscope (TEM) observation was performed in detail to analyze the morphol. of threading dislocations (TDs) in GaN thin layers with various thicknesses. The GaN layers were overgrown on an Al0.28Ga0.72N layer by the metal-org. vapor-phase epitaxy (MOVPE) method. In a GaN layer about 50 nm in thickness, TDs running up in the AlGaN layer pass into the GaN layer and most of them reach the top surface without bending. In thicker GaN layers, on the other hand, many of TDs form a hairpin-configuration on or above the interface of GaN and AlGaN to be annihilated. This difference in morphol. of TDs indicates that the TDs have moved down inside the GaN layer. Since the formation of hairpins is attributed to a stress-relief, there should be an extra half-plane between the paired TDs. Therefore, the movement of TDs should be of "climb motion". Another example of possible TD movement inside a GaN layer is also described. It is emphasized that the possibility of TD-movements inside the thin film crystal during the growth should be taken into account in anal. of thin-layer growth through the behavior of TDs. Growth of AlGaN/GaN heterostructure on vicinal m-plane free-standing GaN substrates prepared by the Na flux method 査読有り Isobe, Yasuhiro; Iida, Daisuke; Sakakibara, Tatsuyuki; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi; Imade, Mamoru; Kitaoka, Yasuo; et al Physica Status Solidi A 208 巻 ( 5 ) 頁: 1191-1194 2011年5月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We fabricated and characterized AlGaN/GaN heterostructure growth by MOVPE on vicinal m-plane free-standing GaN substrates prepd. by the Na flux method. The miscut angle in the LPE-GaN substrate has a great influence on the surface morphol. and cryst. quality of epitaxial GaN and AlGaN films. In particular, AlGaN/GaN on a 4° miscut-angle LPE-GaN substrate shows large step bunching, small-miscut-angle LPE GaN substrate is essential for fabricating on FET structure with a flat surface. Internal quantum efficiency of whole-composition-range AlGaN multiquantum wells 査読有り Ban, Kazuhito; Yamamoto, Jun-ichi; Takeda, Kenichiro; Ide, Kimiyasu; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi Applied Physics Express 4 巻 ( 5 ) 頁: 052101/1-052101/3 2011年5月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We analyze the internal quantum efficiency (IQE) of whole-compn.-range AlGaN multiquantum wells (MQWs) on AlGaN with various dislocation densities (DDs) by excitation-d.-dependent photoluminescence measurement. IQEs of deep UV/UV (DUV/UV) MQWs are strongly dependent on the DD. IQE with an excess carrier d. of 1 × 1018 cm-3 changes from 4 to 64% when the DD changes from 6 × 109 to 2 × 108 cm-2. This trend is almost the same for DUV/UV MQWs with emission wavelength ranging from 230 to 350 nm. Thus, the redn. of the DD is very important for the realization of a high-IQE DUV/UV active layer. Microstructural analysis of thick AlGaN epilayers using Mg-doped AlN underlying layer 査読有り Nonaka, K.; Asai, T.; Ban, K.; Yamamoto, J.; Iwaya, M.; Takeuchi, T.; Kamiyama, S.; Akasaki, I.; Amano, H.; Wu, Z. H. Physica Status Solidi C 8 巻 ( 5 ) 頁: 1467-1470 2011年5月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) This paper reports the microstructural anal. of 20-μm-thick Al0.5Ga0.5N with improved cryst. quality owing to the use of a Mg-doped AlN underlying layer. The threading dislocation d. in 20-μm-thick Al0.5Ga0.5N on Mg-doped AlN was 8.6 × 108 cm-2, which is about one-fifth lower than that of Al0.5Ga0.5N on an undoped AlN underlying layer. The microstructural anal. was carried out to clarify dislocation behaviors in the Al0.5Ga0.5N layer on the Mg-doped AlN underlying layer. Partial strain relaxation by stacking fault generation in InGaN multiple quantum wells grown on (1-101) semipolar GaN 査読有り Wu, Z. H.; Tanikawa, T.; Murase, T.; Fang, Y.-Y.; Chen, C. Q.; Honda, Y.; Yamaguchi, M.; Amano, H.; Sawaki, N. Applied Physics Letters 98 巻 ( 5 ) 頁: 051902/1-051902/3 2011年5月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) The authors have studied the structural properties and relaxation phenomenon of InGaN multiple quantum wells (QWs) on (1.hivin.101) semipolar GaN templates grown on patterned (001) Si substrates by selective area growth technique. Studies by TEM and x-ray diffraction reciprocal space mapping reveal that QWs emitting light at 540 nm experience significant strain relaxation along the in-plane [1.hivin.10.hivin.2] direction by the generation of an array of basal stacking faults (BSF). The generation of BSFs in 540 nm QWs could be an important factor limiting its luminescence efficiency. Freestanding highly crystalline single crystal AlN substrates grown by a novel closed sublimation method 査読有り Yamakawa, Masayasu; Murata, Kazuki; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi; Azuma, Masanobu Applied Physics Express 4 巻 ( 4 ) 頁: 045503/1-045503/3 2011年4月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We fabricated thick freestanding AlN films by a novel close-spaced sublimation method. The spacing between a sintered AlN polycrystal and a SiC substrate is 1 mm. A Ta ring was used to control the spacing between the AlN polycrystal and the SiC substrate. In addn., a special AlN adhesive was also used to fill in the gap between the AlN polycrystal, the Ta ring, and the SiC substrate. By a combination of these techniques, an AlN growth rate as high as 600 μm/h was achieved. A freestanding AlN layer was obtained by the sublimation of the SiC substrate during the AlN growth. Spontaneous formation of highly regular superlattice structure in InGaN epilayers grown by molecular beam epitaxy 査読有り Wu, Z. H.; Kawai, Y.; Fang, Y.-Y.; Chen, C. Q.; Kondo, H.; Hori, M.; Honda, Y.; Yamaguchi, M.; Amano, H. Applied Physics Letters 98 巻 ( 14 ) 頁: 141905/1-141905/3 2011年3月 詳細を見る 担当区分:筆頭著者 記述言語:英語 掲載種別:研究論文(学術雑誌) Structural properties of thick InGaN layers grown on GaN by plasma-assisted mol. beam epitaxy using two growth rates of 1.0 and 3.6 Å/s have been investigated. A highly regular superlattice (SL) structure formed spontaneously in the film grown at 3.6 Å/s but not in the film grown at 1.0 Å/s. The faster grown film also exhibited superior structural quality, which could be due to the surface roughness suppression caused by kinetic limitation, and the inhibition of the Frank-Read dislocation generation mechanism within the spontaneously formed SL structure. Demonstration of diamond field effect transistors by AlN/diamond heterostructure 査読有り Imura, Masataka; Hayakawa, Ryoma; Watanabe, Ei-Ichiro; Liao, Mei-Yong; Koide, Yasuo; Amano, Hiroshi Physica Status Solidi RRL: 5 巻 ( 3 ) 頁: 125-127. 2011年3月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) This is the first report on an AlN/diamond heterojunction field effect transistor (HFET). The AlN epilayer is grown on oxygen-terminated (111) diamond substrates using metalorg. vapor phase epitaxy at a temp. as high as 1240 °C. The transistor and gate capacitance-voltage characteristics indicate that the HFET behaves as a p-channel FET with a normally-on depletion mode. The HFET channel is located at the AlN/diamond interface, and holes are accumulated in diamond close to the interface. The development of the AlN/diamond HFET creates a new possibility for diamond-based power electronics. Role of nonradiative recombination centers and extended defects in nonpolar GaN on light emission efficiency 査読有り Polyakov, A. Y.; Smirnov, N. B.; Govorkov, A. V.; Amano, H.; Pearton, S. J.; Lee, I.-H.; Sun, Q.; Han, J.; Karpov, S. Yu. Applied Physics Letters 98 巻 ( 7 ) 頁: 072104/1-072104/3 2011年2月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) The correlation of integrated microcathodoluminescence efficiency with cryst. quality and deep trap d. of nonpolar GaN films grown by metal org. CVD on semi-insulating 6H-m-SiC or r-sapphire is analyzed. The results suggest a strong influence of nonradiative recombination centers whose concn. decreases with decreased d. of extended defects. Electron traps with energy levels at Ec-0.6 eV and which pin the Fermi level in films with high defect d. are the most likely candidates for the decrease in light emission efficiency in nonpolar GaN. GaInN-based solar cells using strained-layer GaInN/GaInN superlattice active layer on a freestanding GaN substrate 査読有り Kuwahara, Yousuke; Fujii, Takahiro; Sugiyama, Toru; Iida, Daisuke; Isobe, Yasuhiro; Fujiyama, Yasuharu; Morita, Yoshiki; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi, Amano Hiroshi; et al Applied Physics Express 4 巻 ( 2 ) 頁: 021001/1-021001/3 2011年2月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) High-performance GaInN-based solar cells with high open-circuit voltage, high short-circuit c.d., and good fill factor have been obtained using a combination of two different GaInN superlattice structures. The GaInN barrier thicknesses (3 and 0.6 nm) in both superlattice structures were optimized, resulting in a thick GaInN-based active layer with a low pit d. in the device. The conversion efficiency is 2.5% under a solar simulator of air-mass 1.5G and an irradn. intensity of 155 mW/cm2. Internal quantum efficiency and internal loss of ultraviolet laser diodes on the low dislocation density AlGaN underlying layer 査読有り Takeda, Kenichiro; Nagata, Kengo; Ichikawa, Tomoki; Nonaka, Kentaro; Ogiso, Yuji; Oshimura, Yoshinori; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; et al Physica Status Solidi C 8 巻 ( 2 ) 頁: 464-466 2011年2月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We fabricated and evaluated GaN/AlGaN multi-quantum wells (MQWs) and UV laser diodes (UV LDs) on high and low dislocation d. underlying layers by epitaxial lateral overgrowth (ELO) method. We analyzed the internal quantum efficiency (IQE) vs. carrier concn. characteristics quant. by excitation intensity dependent photoluminescence method. The IQE of the MQWs on the ELO AlGaN is 75% when the carrier d. is 1 × 1019 cm-3. We demonstrated the UV LD on the ELO AlGaN. However, the UV LD on flat AlGaN did not operate. Also, we investigated the internal loss (α1) and the IQE multiplied the injection efficiency by changing the reflectivity of the facets. The results showed that the internal loss is 6 cm-1, and the IQE multiplied by the injection efficiency is 18% Drastic reduction of dislocation density in semipolar (11-.22) GaN stripe crystal on Si substrate by dual selective metal-organic vapor phase epitaxy 査読有り Murase, Tasuku; Tanikawa, Tomoyuki; Honda, Yoshio; Yamaguchi, Masahito; Amano, Hiroshi; Sawaki, Nobuhiko Japanese Journal of Applied Physics 50 巻 ( 1 ) 頁: 01AD04/1-01AD04/3. 2011年1月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) A drastic redn. of the dislocation d. in a semipolar (11.hivin.22) GaN stripe on a patterned Si substrate was achieved by the 2-step selective growth of a GaN stripe. After depositing a SiO2 mask on the (11.hivin.22) and (000.hivin.1) faces of a GaN stripe grown on a (113) Si substrate, GaN was regrown only on the (.hivin.1.hivin.122) face. The dislocation d. estd. from the dark-spot d. in a cathodoluminescence (CL) image greatly decreased from 4.0 × 108 to 1.0 × 105/cm2 in the regrowth region. A TEM image also verified that there were no dislocations at the regrowth interfaces. High-temperature operation of normally off-mode AlGaN/GaN heterostructure field-effect transistors with p-GaN gate 査読有り Sugiyama, Takayuki; Amano, Hiroshi; Iida, Daisuke; Iwaya, Motoaki; Kamiyama, Satoshi; Akasaki, Isamu Japanese Journal of Applied Physics 50 巻 ( 1 ) 頁: 01AD03/1-01AD03/3 2011年1月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We demonstrated the high-temp. operation of normally off-mode heterostructure field-effect transistors (HFETs) with a p-GaN gate. The HFETs with a p-GaN gate were operated in the normally off mode at 350 °C. The temperture dependence of their performance was compared with the results of simulation. MBE-VLS growth of catalyst-free III-V axial heterostructure nanowires on (1 1 1)Si substrates 査読有り Paek, Jihyun; Yamaguchi, Masahito; Amano, Hiroshi Journal of Crystal Growth 323 巻 ( 1 ) 頁: 315-318 2011年1月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) For application in novel opto-electronic nanowire devices, Ga-assisted GaAs/InxGa1-xAs axial heterostructure nanowires grown on a (1 1 1)Si substrate at a high In/Ga flux ratio were investigated. The increased diam. of the InxGa1-xAs region of the nanowire was obsd. from a SEM image. The In compn. of 0.01-0.02 of the InxGa1-xAs was shown by EDX point anal. The In concn. of 0.62 of an In-Ga alloy droplet was estd. from the diam. ratio of the InxGa1-xAs/GaAs region. From these results, it was considered that the excess In was collected in the droplet, resulting in an increased nanowire diam. The increased diam. of the InxGa1-xAs region was also discussed together with the results of thermodn. calcn. Microstructures of GaInN/GaInN superlattices on GaN substrates 査読有り Sugiyama, Toru; Kuwahara, Yosuke; Isobe, Yasuhiro; Fujii, Takahiro; Nonaka, Kentaro; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi Applied Physics Express 4 巻 ( 1 ) 頁: 015701/1-015701/3. 2011年1月 詳細を見る 担当区分:筆頭著者 記述言語:英語 掲載種別:研究論文(学術雑誌) We found different behaviors of misfit dislocations in a Ga0.83In0.17N single layer and in Ga0.83In0.17N/Ga0.93In0.07N superlattices, both on GaN substrates. In the case of the single layer, misfit dislocations were formed at the GaInN/GaN interfaces and extended through the GaInN layer to the surface. In contrast, the misfit dislocations in the superlattices are bent laterally at interfaces between the Ga0.83In0.17N and Ga0.93In0.07N layers. In addn., most of the dislocations do not reach the surface owing to the formation of dislocation loops. As a result, the dislocation d. at the surface of the GaInN superlattice sample was 5 × 107 cm-2. Realization of nitride-based solar cell on freestanding GaN substrate 査読有り Kuwahara, Yosuke; Fujii, Takahiro; Fujiyama, Yasuharu; Sugiyama, Tohru; Iwaya, Motoaki; Takeuchi, Tetsuya; Kamiyama, Satoshi; Akasaki, Isamu; Amano, Hiroshi Applied Physics Express 3 巻 ( 11 ) 頁: 111001/1-111001/3 2010年11月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) A p-i-n solar cell composed of an undoped GaInN layer sandwiched between n- and p-type GaN layers was grown on a freestanding c-plane GaN substrate and a c-plane sapphire substrate covered with a low-temp.-deposited buffer layer. The open-circuit voltage is 2.23 V, the fill factor is 61%, the short-circuit c.d. is 1.59 mA/cm2, and the conversion efficiency of the solar cell on the GaN substrate is 1.41% using a solar simulator (1.5 suns). Compared with the solar cell characteristics of the device grown on the sapphire substrate, pit d. markedly decreases. As a result, shunt resistance increases, suppressing the open-circuit voltage drop. Strain relaxation mechanisms in AlGaN epitaxy on AlN templates 査読有り Wu, Zhihao; Nonaka, Kentaro; Kawal, Yohjiro; Asai, Toshiaki; Ponce, Fernando A.; Chen, Changqing; Iwaya, Motoaki; Kamiyama, Satoshi; Amano, Hiroshi; Akasaki, Isamu Applied Physics Express 3 巻 ( 11 ) 頁: 111003/1-111003/3 2010年11月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Two strain relaxation processes have been obsd. in AGaN layers grown on thick AlN templates. In Process I, a type threading dislocations (TDs) with b = 1/3.ltbbrac.11.hivin.20.rtbbrac. from the AlN underlayer are inclined away from the [0001] axis toward the .ltbbrac.1.hivin.100.rtbbrac. directions when they enter the AlGaN film, forming dislocation line projection perpendicular to the Burger vector. In Process II, a + c-type TDs from the AlN underlayer with Burgers vector of b = 1/3.ltbbrac.11.hivin.23.rtbbrac. glide on {0.hivin.111} planes when they enter the AlGaN film to generate interfacial misfit dislocations lying along the .ltbbrac..hivin.2110.rtbbrac. directions at the AlGaN/AlN interface. Temperature dependence of normally off mode AlGaN/GaN heterostructure field-effect transistors with p-GaN gate 査読有り Sugiyama, Takayuki; Iida, Daisuke; Iwaya, Motoaki; Kamiyama, Satoshi; Amano, Hiroshi; Akasaki, Isamu Physica Status Solidi C: 7 巻 ( 10 ) 頁: 2419-2422 2010年10月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We demonstrated high-temp. operation of normally off-mode junction-heterostructure-field-effect transistors (JHFETs) with a p-GaN gate that shows a very small shift of the threshold voltage against ambient temp. Distinct normally off-mode operation with a max. drain current of 93.2 mA/mm at 300 °C was realized. Therefore, normally off-mode GaN-based JFETs are greatly superior to Si-based devices as high-temp. switching devices. Analysis of polar direction of AlN grown on (0001) sapphire and 6H-SiC substrates by high-temperature metal-organic vapor phase epitaxy using coaxial impact collision ion scattering spectroscopy 査読有り Imura, Masataka; Ohnishi, Tsuyoshi; Sumiya, Masatomo; Liao, Meiyong; Koide, Yasuo; Amano, Hiroshi; Lippmaa, Mikk Physica Status Solidi C 7 巻 ( 10 ) 頁: 2365-2367 2010年10月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) High-cryst. quality AlN layers with an atomically flat surface are grown on (0001) sapphire and 6H-SiC substrates by metal-org. vapor phase epitaxy at 1400 °C without low-temp. buffer layer. The polar direction of AlN layers is investigated by coaxial impact-collision ion scattering spectroscopy (CAICISS). For AlN growth on sapphire substrate, trimethylaluminum (TMAI) is supplied for 10 s before introducing ammonia (NH3). For AlN growth on SiC substrate, TMAl and NH3 are supplied at the same time. The CAICISS spectrum of AlN layers is analyzed by measuring the dependence of the Al atoms signal intensity on the angle of ion beam incidence considering the shadowing and focusing effects for detg. the polar direction of AlN layers. The CAICISS spectra clearly indicate the polar direction of AlN layers and both AlN layers are found to be had the Al-polarity. Atomic layer epitaxy of AlGaN 査読有り Nagamatsu, Kentaro; Iida, Daisuke; Takeda, Kenichiro; Nagata, Kensuke; Asai, Toshiaki; Iwaya, Motoaki; Kamiyama, Satoshi; Amano, Hiroshi; Akasaki, Isamu Physica Status Solidi C: 7 巻 ( 10 ) 頁: 2368-2370 2010年10月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Atomic layer epitaxy of AlGaN with an av. growth rate of as high as 4.5 mm/h has been achieved by the high-speed switching-valves (HSSVs) technique in a raised-pressure metalorg. vapor phase epitaxy system. Regarding the duration of group III metalorgs. and NH3 gases input, 0.1 s for each injection time is found to be sufficient to realize AlGaN growth of one monolayer per cycle over a 2-in. wafer with hydrogen and nitrogen carrier gases at a raised pressure. Low-temp. growth of high-quality AlGaN has been achieved using HSSVs. GaInN/GaN p-i-n light-emitting solar cells 査読有り Fujiyama, Y.; Kuwahara, Y.; Iwaya, M.; Kamiyama, S.; Amano, H.; Akasaki, I. Physica Status Solidi C 7 巻 ( 10 ) 頁: 2382-2385. 2010年10月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) GaInN/GaN p-i-n double-heterojunction structures were grown by metal-org. vapor phase epitaxy on c-plane sapphire substrates, and light-emitting solar cells with different GaInN active layer thicknesses were fabricated. The thickness of the GaInN active layer was varied from 100 to 400 nm, while the thickness of both n-type and p-type GaN layers was kept const. A semitransparent ohmic contact to p-type GaN was formed by electron-beam evapn. of Ni/Au (5 nm/5 nm). The film thickness of p-GaN was 50 nm. The external quantum efficiency (EQE) of the device with a 400 nm GaInN layer exceeded 60% at a wavelength of approx. 380 nm. The transparency of the Ni/Au electrode was 68%. Therefore, the internal quantum efficiency of this device exceeded 95%. Note that this device emitted green light when a forward voltage was applied. The electroluminescence peak wavelength was approx. 525 nm, which was much longer than the EQE peak wavelength. The origin of this large emission shift is discussed. Threshold voltage control using SiNx in normally off AlGaN/GaN HFET with p-GaN gate 査読有り Sugiyama, T.; Iida, D.; Iwaya, M.; Kamiyama, S.; Amano, H.; Akasaki, I. Physica Status Solidi C 7 巻 ( 7-8 ) 頁: 1980-1982 2010年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) The threshold voltage (Vth) of normally off-mode AlGaN/GaN junction heterostructure field-effect transistors with a p-type GaN gate can be successfully controlled by inserting a SiNx insulator between the p-GaN and a Ni/Au electrode. The Vth can be controlled from +1 V to above +8 V. Moreover, the gate leakage current of transistors decreases and their gate voltage at which gate current steeply increases becomes higher. The mechanism of the threshold voltage change is analyzed by the equiv. circuit model. AlGaN/GaN HFETs on Fe-doped GaN substrates 査読有り Oshimura, Yoshinori; Takeda, Kenichiro; Sugiyama, Takayuki; Iwaya, Motoaki; Kamiyama, Satoshi; Amano, Hiroshi; Akasaki, Isamu; Bandoh, Akira; Udagawa, Takashi Physica Status Solidi C 7 巻 ( 7-8 ) 頁: 1974-1976 2010年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) AlGaN/GaN HFETs with different undoped GaN thicknesses were grown on Fe-doped freestanding GaN substrates by conventional MOVPE. To realize a high drain current, thick undoped GaN is found to be necessary. SIMS measurement shows that Fe is redistributed into the epilayer, by which the scattering center is generated at the channel when the thickness of the undoped GaN is insufficient. We also obsd. a similar Fe profile in the GaN/sapphire template placed on the side of the Fe-doped GaN substrate during growth. Therefore, Fe in the Fe-doped GaN substrate is redistributed not only through a solid but also through vapor. Growth and characterization of GaN grown on moth-eye patterned sapphire substrates 査読有り Ishihara, Akihiro; Kawai, Ryousuke; Kitano, Thukasa; Suzuki, Atushi; Kondo, Toshiyuki; Iwaya, Motoaki; Amano, Hiroshi; Kamiyama, Satoshi; Akasaki, Isamu Physica Status Solidi C 7 巻 ( 7-8 ) 頁: 2056-2058 2010年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) To realize high-efficiency light-emitting diodes (LEDs), it is necessary to increase light extn. efficiency. Therefore, the introduction of a moth-eye structure, which consists of periodic cones with a pitch of optical wavelength magnitude, into a sapphire surface before the epitaxial growth of nitride films is very promising for reducing the reflectivity of light resulting in high light extn. efficiency. 450 nm GaInN/GaN LEDs were fabricated on conventional and moth-eye substrates by metal org. vapor phase epitaxy (MOVPE). The intensity of room-temp. photoluminescence emitted from the LED with the moth-eye-patterned sapphire substrate was 1.6 times higher than that emitted from the LED without the moth-eye substrate. Under a current injection of 50 mA, the output power of the moth-eye LED is 3.6 times higher than that of the conventional LED.~0 Citings Growth of GaInN by raised-pressure metalorganic vapor phase epitaxy 査読有り Iida, Daisuke; Nagata, Kensuke; Makino, Takafumi; Iwaya, Motoaki; Kamiyama, Satoshi; Amano, Hiroshi; Akasaki, Isamu; Bandoh, Akira; Udagawa, Takashi Applied Physics Express 3 巻 ( 7 ) 頁: 075601/1-075601/2 2010年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Growth of low-dislocation-density AlGaN using Mg-doped AlN underlying layer 査読有り Asai, T.; Nonaka, K.; Ban, K.; Nagata, K.; Nagamatsu, K.; Iwaya, M.; Kamiyama, S.; Amano, H.; Akasaki, I. Physica Status Solidi C 7 巻 ( 7-8 ) 頁: 2101-2103 2010年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We report on a new technol. for growing low-dislocation-d. AlGaN in which a Mg-doped AlN underlying layer is used. By growing AlxGa1-xN on AlN:Mg with AlN molar fractions x of 0.3, 0.5 and 0.7, the d. of misfit dislocations is much reduced compared with that in the case of growing AlGaN on undoped AlN. In addn., the surface becomes atomically flat. Internal quantum efficiency of GaN/AlGaN-based multi quantum wells on different dislocation densities underlying layers 査読有り Takeda, Kenichiro; Mori, Fumiaki; Ogiso, Yuji; Ichikawa, Tomoaki; Nonaka, Kentaro; Iwaya, Motoaki; Kamiyama, Satoshi; Amano, Hiroshi; Akasaki, Isamu Physica Status Solidi C 7 巻 ( 7-8 ) 頁: 1916-1918 2010年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Internal quantum efficiency (IQE) of GaN/AlGaN multi quantum wells on the low dislocation d. Al0.25Ga0.75N grown by epitaxial lateral overgrowth (ELO) and facet controlled epitaxial lateral overgrowth were investigated by excitation intensity dependent photoluminescence measurement. The threading dislocation d. decreased from 4 × 109cm-2 to 2 × 108 cm-2 by using ELO method, then the IQE was much improved from 5% to 40% when the carrier d. was 1 × 1018 cm-3. Mg-related acceptors in GaN 査読有り Monemar, B.; Paskov, P. P.; Pozina, G.; Hemmingsson, C.; Bergman, J. P.; Amano, H.; Akasaki, I.; Figge, S.; Hommel, D.; et al. Physica Status Solidi C 7 巻 ( 7-8 ) 頁: 1850-1852 2010年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Photoluminescence spectra of c-plane Mg doped GaN samples grown by MOVPE on bulk GaN templates reveal previously unknown properties, like the presence of several Mg-related acceptors. The use of unstrained samples allows a study of both bound exciton (BE) and donor-acceptor pair (DAP) spectra. Two main acceptors A1 and A2 are obsd. strongly in BE spectra as well as in DAP spectra, they have similar binding energies, i.e. about 220 meV. The common assignment of the deeper blue PL emission at 2.8-3.0 eV to a deep donor-shallow acceptor transition is questioned, and discussed in connection with the compensation problem in p-GaN. It seems like the Fermi level in p-GaN is controlled by a set of Mg-related acceptors at energies 0.2-0.6 eV from the valence band top. Nitride-based light-emitting solar cell 査読有り Kuwahara, Y.; Fujiyama Y; Iwaya, M.; Kamiyama, S.; Amano, H.; Akasaki, I Physica Status Solidi C 7 巻 ( 7-8 ) 頁: 1807-1809 2010年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We report on the characteristics of a group-III-nitride-based solar cell. A GaInN/GaN double heterojunction p-i-n solar cell composed of a GaInN active layer sandwiched between n-type and p-type GaN layers was grown by metal-org. vapor phase epitaxy through an undoped GaN layer on (0001) sapphire substrate. The InN molar fraction of the GaInN active layer was detd. to be 11% from a secondary ion mass spectrometry profile. The max. external quantum efficiency reached 65%, and the internal quantum efficiency was 95% or more. This device emitted light after forward current injection. The PL peak almost corresponded to the absorption edge. However, the electroluminescence (EL) peak was at the wavelength much longer than the absorption edge. The open-circuit voltage is 1.51 V, the fill factor is 52%, and the short-circuit c.d. is 1.6 mA/cm2. Study of two-dimensional electron gas in AlGaN channel HEMTs with high crystalline quality 査読有り Hashimoto, Shin; Akita, Katsushi; Tanabe, Tatsuya; Nakahata, Hideaki; Takeda, Kenichiro; Amano, Hiroshi Physica Status Solidi C 7 巻 ( 7-8 ) 頁: 1938-1940 2010年7月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Epitaxial structures of AlGaN channel high electron mobility transistors (HEMTs) were grown on sapphire and AlN substrates. Redn. in the full width at half max. of X-ray rocking curve for (10-12) peak of the AlGaN channel layer owing to the redn. of threading dislocation densities resulted in a sharp decrease in the sheet resistance of 2-dimensional electron gas (2DEG). In the case of AlGaN channel HEMTs, it was found that improvement of the cryst. quality of AlGaN channel layers is essential to the redn. of the sheet resistance of 2DEG. The use of AlN substrates resulted in improved cryst. quality of the AlGaN layer and lower 2DEG resistance, suggesting the high potential of AlN substrates for AlGaN channel HEMTs. Improved efficiency of 255-280 nm AlGaN-based light-emitting diodes 査読有り Pernot, Cyril; Kim, Myunghee; Fukahori, Shinya; Inazu, Tetsuhiko; Fujita, Takehiko; Nagasawa, Yosuke; Hirano, Akira; Ippommatsu, Masamichi; Iwaya, Motoaki; Kamiyama, Satoshi,Hiroshi Amano et al Applied Physics Express 3 巻 ( 6 ) 頁: 061004/1-061004/3 2010年6月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We report on the fabrication and characterization of AlGaN-based deep UV light-emitting diodes (LEDs) with the emission wavelength ranging from 255-280 nm depending on the Al compn. of the active region. The LEDs were flip-chip bonded and achieved external quantum efficiencies of over 3% for all investigated wavelengths. Under cw operation, an output power of more than 1 mW at 10 mA was demonstrated. A moth-eye structure was fabricated on the back side of the Al2O3 substrate, and on-wafer output power measurement indicated a 1.5-fold improvement of light extn. Compensation effect of Mg-doped a- and c-plane GaN films grown by metalorganic vapor phase epitaxy 査読有り Iida, Daisuke; Tamura, Kenta; Iwaya, Motoaki; Kamiyama, Satoshi; Amano, Hiroshi; Akasaki, Isamu Journal of Crystal Growth 312 巻 ( 21 ) 頁: 3131-3135. 2010年6月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) The elec. and optical properties of Mg-doped a- and c-plane GaN films grown by MOVPE were systematically investigated. The photoluminescence spectra of Mg-doped a- and c-plane GaN films exhibit strong emissions related to deep donors when Mg doping concns. are above 1 × 1020 cm-3 and 5 × 1019 cm-3, resp. The elec. properties also indicate the existence of compensating donors because the hole concn. decreases at such high Mg doping concns. In addn., we estd. the ND/NA compensation ratio of a- and c-plane GaN by variable-temp. Hall effect measurement. The obtained results indicate that the compensation effect of the Mg-doped a-plane GaN films is lower than that of the Mg-doped c-plane GaN films. Misfit strain relaxation in m-plane epitaxy of InGaN on ZnO 査読有り Wu, Z. H.; Sun, K. W.; Wei, Q. Y.; Fischer, A. M.; Ponce, F. A.; Kawai, Y.; Iwaya, M.; Kamiyama, S.; Amano, H.; Akasaki, I. Applied Physics Letters 96 巻 ( 7 ) 頁: 071909/1-071909/3 2010年3月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) The microstructure of m-plane InGaN epilayers grown on m-plane ZnO has been found to depend significantly on indium content in the range from 0.07 to 0.17, where anisotropic lattice mismatch between InGaN and ZnO results in decreasingly tensile and increasingly compressive stress along the a and c lattice axes. For indium content below 0.10, periodic arrays of misfit dislocations with a Burgers vector of 1/3[11-20] are obsd. parallel to the [0001] direction. For indium content above 0.12, generation of basal-plane stacking faults relieve the compressive stress along the 0001 direction. These characteristic mechanisms of strain relaxation should provide new approaches to engineer thick InGaN layers with reduced lattice misfit strain. Microstructure of AlN with two-domain structure on (001) diamond substrate grown by metal-organic vapor phase epitaxy 査読有り Imura, Masataka, Nakajima, Kiyomi, Liao, Meiyong, Koide, Yasuo, Amano, Hiroshi Diamond and Related Materials 19 巻 ( 0 ) 頁: 131-133 2010年2月 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) We investigate the microstructures of domain boundaries in an AlN layer grown on a (001) diamond substrate by metal-org. vapor phase epitaxy. The AlN layer has a two-domain structure with crystal orientation along either <112-0> AlN [named by AlNI domain] or <101-0> AlN [named by AlNII domain] parallel to [110] direction of diamond. The AlNI and AlNII domains are not atomically bonded at two-domain boundary from initial to final step of growth, while an edge-type dislocation is generated at single-domain boundary (SDB). In addn., an inversion AlNI domain [named by AlNI*] is randomly-ordered at the initial stage of the coalescence between the AlNI domains. The AlNI* is easily terminated with increasing the thickness of AlNI domain. The inversion domain boundary changes to the edge-type dislocation at the SDB with further growth, which reduces the defect d. in the AlNI domains. High-output-power AlGaN/GaN ultraviolet-light-emitting diodes by activation of Mg-doped p-type AlGaN in oxygen ambient 査読有り Nagata, Kengo, Ichikawa, Tomoki, Takeda, Kenichiro, Nagamatsu, Kentaro, Iwaya, Motoaki, Kamiyama, Satoshi, Amano, Hiroshi, Akasaki, Isamu Physica Status Solidi A: 207 巻 ( 0 ) 頁: 1393-1396 2010年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) MOVPE法により成長したa面及びc面MgドープGaNにおける補償効果 査読有り 飯田大輔、田村健太、岩谷素顕、天野浩、上山智、赤﨑勇 312 巻 ( 21 ) 頁: 3131-3135 2010年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Defects in highly Mg-doped AlN 査読有り Nonaka, Kentaro, Asai, Toshiaki, Nagamatsu, Kentaro, Iwaya, Motoaki, Kamiyama, Satoshi, Amano, Hiroshi, Akasaki, Isamu Physica Status Solidi A 207 巻 ( 0 ) 頁: 1299-1301 2010年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Growth mechanism of c-axis-oriented AlN on (001) diamond substrates by metal-organic vapor phase epitaxy 査読有り Imura, Masataka, Nakajima, Kiyomi, Liao, Meiyong, Koide, Yasuo, Amano, Hiroshi Journal of Crystal Growth 312 巻 ( 0 ) 頁: 368-372 2010年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Growth mechanism of c-axis-oriented AlN on (111) diamond substrates by metal-organic vapor phase epitaxy 査読有り Imura, Masataka, Nakajima, Kiyomi, Liao, Meiyong, Koide, Yasuo, Amano, Hiroshi Journal of Crystal Growth 312 巻 ( 0 ) 頁: 1325-1328 2010年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) III族窒化物半導体へのp型ドーピングと結晶欠陥 招待有り 査読有り 天野 浩、岩谷 素顕、上山 智、赤﨑 勇 日本結晶成長学会誌 36 巻 ( 3 ) 頁: 200-204 2009年3月 詳細を見る 担当区分:筆頭著者 記述言語:日本語 掲載種別:研究論文(学術雑誌) GaNおよびAlGaNにおけるMgアクセプタの挙動の詳細を明らかにした。 Temperature dependence of excitonic transitions in a-plane AlN epitaxial layers 査読有り Murotani, Hideaki, Kuronaka, Takahiro, Yamada, Yoichi, Taguchi, Tsunemasa, Okada, Narihito, Amano, Hiroshi Journal of Applied Physics 105 巻 ( 0 ) 頁: 083533/1-083533/6 2009年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Activation energy of Mg in a-plane Ga1-xInxN (0 < x < 0.17) 査読有り Iida, Daisuke, Iwaya, Motoaki, Kamiyama, Satoshi, Amano, Hiroshi, Akasaki, Isamu Physica Status Solidi B: 246 巻 ( 0 ) 頁: 1188-1190 2009年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Crystal growth and p-type conductivity control of AlGaN for high-efficiency nitride-based UV emitters 査読有り Mori, T., Nagamatsu, K., Nonaka, K., Takeda, K., Iwaya, M., Kamiyama, S., Amano, H., Akasaki, I. Physica Status Solidi C 6 巻 ( 0 ) 頁: 2621-2625 2009年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Electrical properties and deep traps spectra in undoped and Si-doped m-plane GaN films 査読有り Polyakov, A. Y., Smirnov, N. B., Govorkov, A. V., Markov, A. V., Yugova, T. G., Petrova, E. A., Amano, H., Kawashima, T., Scherbatchev, K. D., Bublik, V. T. Journal of Applied Physics 105 巻 ( 0 ) 頁: 063708/1-063708/9 2009年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Electrical properties and deep traps spectra in undoped M-plane GaN films prepared by standard MOCVD and by selective lateral overgrowth 査読有り Polyakov, A. Y., Smirnov, N. B., Govorkov, A. V., Markov, A. V., Yakimov, E. B., Vergeles, P. S., Amano, H., Kawashima, T. Journal of Crystal Growth 311 巻 ( 0 ) 頁: 2923-2925 2009年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Evidence for two Mg related acceptors in GaN 査読有り Monemar B, Paskov P P, Pozina G, Hemmingsson C, Bergman J P, Kawashima T, Amano H, Akasaki I, Paskova T, Figge S, et al Physical review letters 102 巻 ( 0 ) 頁: 235501/1-235501/4 2009年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Experimental and theoretical investigations of optical properties of GaN/AlGaN MQW nanostructures. Impact of built-in polarization fields 査読有り Esmaeili, M., Gholami, M., Haratizadeh, H., Monemar, B., Holtz, P. O., Kamiyama, S., Amano, H., Akasaki, I. Opto-Electronics Review 17 巻 ( 0 ) 頁: 293-299 2009年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Growth of thick GaInN on grooved (1011) GaN/(1012) 4H-SiC 査読有り Matsubara, Tetsuya, Senda, Ryota, Iida, Daisuke, Iwaya, Motoaki, Kamiyama, Satoshi, Amano, Hiroshi, Akasaki, Isamu Journal of Crystal Growth 311 巻 ( 0 ) 頁: 2926-2928 2009年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) High-performance UV emitter grown on high-crystalline-quality AlGaN underlying layer 査読有り Tsuzuki, Hirotoshi, Mori, Fumiaki, Takeda, Kenichiro, Ichikawa, Tomoki, Iwaya, Motoaki, Kamiyama, Satoshi, Amano, Hiroshi, Akasaki, Isamu, Yoshida, Harumasa, Kuwabara, Masakazu, et al Physica Status Solidi A 206 巻 ( 0 ) 頁: 1199-1204 2009年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) InGaN growth with various InN mole fractions on m-plane ZnO substrate by metalorganic vapor phase epitaxy 査読有り Kawai, Yohjiro, Ohsuka, Shinya, Iwaya, Motoaki, Kamiyama, Satoshi, Amano, Hiroshi, Akasaki, Isamu Journal of Crystal Growth 311 巻 ( 0 ) 頁: 2929-2932 2009年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Misfit strain relaxation by stacking fault generation in InGaN quantum wells grown on m-plane GaN 査読有り Fischer, Alec M., Wu, Zhihao, Sun, Kewei, Wei, Qiyuan, Huang, Yu, Senda, Ryota, Iida, Daisuke, Iwaya, Motoaki, Amano, Hiroshi, Ponce, Fernando A. Applied Physics Express 2 巻 ( 0 ) 頁: 041002/1-041002/3 2009年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Novel UV devices on high-quality AlGaN using grooved underlying layer 査読有り Tsuzuki, Hirotoshi, Mori, Fumiaki, Takeda, Kenichiro, Iwaya, Motoaki, Kamiyama, Satoshi, Amano, Hiroshi, Akasaki, Isamu, Yoshida, Harumasa, Kuwabara, Masakazu, Yamashita, Yoji, et al Journal of Crystal Growth 311 巻 ( 0 ) 頁: 2860-2863 2009年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) One-sidewall-seeded epitaxial lateral overgrowth of a-plane GaN by metalorganic vapor-phase epitaxy 査読有り Iida, Daisuke, Iwaya, Motoaki, Kamiyama, Satoshi, Amano, Hiroshi, Akasaki, Isamu Journal of Crystal Growth 311 巻 ( 0 ) 頁: 2887-2890 2009年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Optimization of electrode configuration in large GaInN light-emitting diodes 査読有り Ochiai, Wataru, Kawai, Ryosuke, Suzuki, Atsushi, Iwaya, Motoaki, Amano, Hiroshi, Kamiyama, Satoshi, Akasaki, Isamu Physica Status Solidic 6 巻 ( 0 ) 頁: 1416-1419 2009年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Relaxation and recovery processes of AlxGa1-xN grown on AlN underlying layer 査読有り Asai, Toshiaki, Nagata, Kensuke, Mori, Toshiaki, Nagamatsu, Kentaro, Iwaya, Motoaki, Kamiyama, Satoshi, Amano, Hiroshi, Akasaki, Isamu Journal of Crystal Growth 311 巻 ( 0 ) 頁: 2850-2852 2009年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Strong emission from GaInN/GaN multiple quantum wells on high-crystalline-quality thick m-plane GaInN underlying layer on grooved GaN 査読有り Senda, Ryota, Matsubara, Tetsuya, Iida, Daisuke, Iwaya, Motoaki, Kamiyama, Satoshi, Amano, Hiroshi, Akasaki, Isamu Applied Physics Express 2 巻 ( 0 ) 頁: 061004/1-061004/3 2009年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Impact of high-temperature growth by metal-organic vapor phase epitaxy on microstructure of AlN on 6H-SiC substrates 査読有り Imura Masataka, Sugimura Hiroki, Okada Narihito, Iwaya Motoaki, Kamiyama Satoshi, Amano Hiroshi, Akasaki Isamu, Bandoh Akira J. Crystal Growth 310 巻 ( 0 ) 頁: 2308-2313 2008年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) High-efficiency AlGaN-based UV light-emitting diode on laterally overgrown AlN 査読有り Nagamatsu Kentaro, Okada Narihito, Sugimura Hiroki, Tsuzuki Hirotoshi, Mori Fumiaki, Iida Kazuyoshi, Bando Akira, Iwaya Motoaki, Kamiyama Satoshi, Amano Hiroshi, Akasaki Isamu J. Crystal Growth 310 巻 ( 0 ) 頁: 2326-2329 2008年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) AlN and AlGaN by MOVPE for UV light emitting devices 査読有り Amano, Hiroshi, Imura, Masataka, Iwaya, Motoaki, Kamiyama, Satoshi, Akasaki, Isamu Materials Science Forum 590 巻 ( 0 ) 頁: 175-210 2008年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Breakthroughs in improving crystal quality of GaN and invention of the p-n junction blue-light-emitting diode 査読有り Akasaki, Isamu, Amano, Hiroshi Japanese Journal of Applied Physics 47 巻 ( 0 ) 頁: 3781 2008年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Control of p-type conduction in a-plane Ga1-xInxN (0 < x < 0.10) grown on r-plane sapphire substrate by metalorganic vapor-phase epitaxy 査読有り Iida, Daisuke, Iwaya, Motoaki, Kamiyama, Satoshi, Amano, Hiroshi, Akasaki, Isamu Journal of Crystal Growth 310 巻 ( 0 ) 頁: 4996-4998 2008年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Control of stress and crystalline quality in GaInN films used for green emitters 査読有り Iwaya, Motoaki, Miura, Aya, Senda, Ryota, Nagai, Tetsuya, Kawashima, Takeshi, Iida, Daisuke, Kamiyama, Satoshi, Amano, Hiroshi, Akasaki, Isamu Journal of Crystal Growth 310 巻 ( 0 ) 頁: 4920-4922 2008年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Dynamical study of the radiative recombination processes in GaN/AlGaN QWs 査読有り Sabooni, Mahmood, Esmaeili, Morteza, Haratizadeh, Hamid, Monemar, Bo, Amano, Hiroshi Journal of Materials Science: Materials in Electronics 19 巻 ( 0 ) 頁: S316-S318 2008年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) Effect of annealing on metastable shallow acceptors in Mg-doped GaN layers grown on GaN substrates 査読有り Pozina, G., Hemmingsson, C., Paskov, P. P., Bergman, J. P., Monemar, B., Kawashima, T., Amano, H., Akasaki, I., Usui, A. Applied Physics Letters 92 巻 ( 0 ) 頁: 151904/1-151904/3 2008年 詳細を見る 記述言語:英語 掲載種別:研究論文(学術雑誌) High hole concentration in Mg-doped a-plane Ga1-xInxN (0![](https://dafa888888888.com/img/bg.jpg)