IRE Laboratory

The 6th International Symposium on Growth of III nitrides

Hamamatsu, Act City Hamamatsu

第45回結晶成長国内会議

北海道大学交流会館

2015/10/19-21
RF-MBE 成長法による傾斜組成バッファー層上GaN on Si 成長

2015/10/19-21
RF-MBE 成長法による傾斜組成バッファー層上GaN on Si 成長

Si基板上窒化物半導体デバイス(例えば高出力高周波用HEMTデバイス)を作る方法が検討されている中で、RF-MBE法は省材料成長法であり,その開発が期待される。Si(111)基板を窒素原子で窒化するIRE(Interface reaction epitaxy: 界面反応エピタキシャル)法によるβ-Si3N4成長に続いて、Al照射IRE法によりAlNのDBL (double buffer layer)を作り、さらにAM-MEE (an activity modulation migration enhanced epitaxy ) 法でAl1-xGaxN ( x= 0 to 1)組成を傾斜的に変化させてGaN組成とした後、GaN薄膜を成長させるGaN on Si (GoS)成長条件の最適化を調べた。

ナノ構造・エピタキシャル成長分科会 2015年春季講演会

日本結晶成長学会 7回 窒化物半導体結晶成長講演会(プレISGN-6)
片平さくらホール(東北大学片平キャンパス)

2015/5/7-8
Si 上AlN ダブルバッファ層の界面反応エピタキシャル成長と RF-MBE 法成長AlN on Si 膜のXRD 評価

2015/5/7-8
Si 上AlN ダブルバッファ層の界面反応エピタキシャル成長と RF-MBE 法成長AlN on Si 膜のXRD 評価

Si基板から窒化物半導体デバイスまでを作る方法として、13.56MHz高周波放電を用いるRF-MBE法は省材料成長であり,GaN on Si(GoS)には最も適した成長法と考えられる。Si(111)基板を窒素原子による窒化のIRE(Interface reaction epitaxy: 界面反応エピタキシャル)法に続いて、Al照射とIRE法によりAlNのDBL (double buffer layer)を作り、AM-MEE (an activity modulation migration enhanced epitaxy ) 法によりGoS基板となる高品質AlN on Si(AoS)膜を得る実験を行った。

第44回結晶成長国内会議(NCCG−44)

学習院創立百年記念会館

2014/11/6-8
RF-MBE 成長法によるSi(111)上AlN 成長
-ダブルバッファ層成長とAM-MEE 法成長膜厚依存性-

2014/11/6-8
RF-MBE 成長法によるSi(111)上AlN 成長
-ダブルバッファ層成長とAM-MEE 法成長膜厚依存性-

Thickness dependence of FWHM of XRD of AlN(0001) grown on Si(111) by a radiofrequency discharge molecular beam
epitaxy (RF-MBE) was studied to grow high quality AlN films. Interference fringe observation on 2theta-omega scan for
thin-high-quality AlN on Si (AoS) films showed growth of nearly perfect crystal of AlN on Si substrate.

ISPlasma2014

第43回結晶成長国内会議 NCCG-43 Nagano

2013/11/6-8
RF-MBE成長におけるSi(111)上AlNダブルバッファ層成長における界面反応エピタキシャル成長IRE法β-Si3N4膜

2013/11/6-8
RF-MBE成長におけるSi(111)上AlNダブルバッファ層成長における界面反応エピタキシャル成長IRE法β-Si3N4膜

高周波分子線エピタキシー法(RF-MBE)により成長させたSi(111)上に成長させたAlN(0001)(AoS)のXRDの半値幅の厚み依存性を良質なAlN膜を成長させる目的で調べた。2θ-ωのXRD測定で膜厚による干渉効果が観察され、膜の良質性がしめされた。

JSAP-MRS joint symposium J-section

2013/09/16-20
JSAP-MRS joint symposium J-section発表

2013/09/16-20
JSAP-MRS joint symposium J-section発表

アブストラクトとポスター
Interface Reaction Epitaxial (IRE) Growth and Double Buffer Layer (DBL) of AlN on Si using PA-MBE

STARCワークショップ2013

第17回結晶成長国際会議(ICCGE-17)

2013/08/11-18
ポーランドワルシャワで開催の第17回結晶成長国際会議(ICCGE-17)参加

2013/08/11-18
ポーランドワルシャワで開催の第17回結晶成長国際会議(ICCGE-17)参加

Activity modulation and role of nitrogen radicals in RF-MBE for growth of group III nitrides and their alloys
ポスター発表をしました。
ICCGE-17においてIRE研究所の展示を行い、京田辺市の展示出展事業の補助金を受けた。

ISPlasma2013

2013年1月29日~2月1日
AM-MEEによるIII族窒化物成長の原理を報告した。

2013年1月29日~2月1日
AM-MEEによるIII族窒化物成長の原理を報告した。

Activity modulation MEE growth of group III nitrides on Si(111) using PA-MBE

資料を見る (PDF:221KB) ポスターを見る(PDF:392KB)

島屋ベンチャーフェスタ2012

2012年11月15日~16日
大阪産業創造館(通称 産創館)にてポスター発表と講演を行った。

2012年11月15日~16日
大阪産業創造館(通称 産創館)にてポスター発表と講演を行った。

関西では老舗のテクニカルインキュベーション施設の島屋ベンチャーインキュベーターの主催で11月15日(木)16日(金)の両日、大阪産業創造館(通称 産創館)にて島屋ベンチャーフェスタ2012が開催され、ポスター発表と講演を行った。

プレゼン資料を見る(PDF:2,300KB)ポスターを見る(PDF:1,121KB)

第42回結晶成長国内会議(NCCG=42)

ビジネスフェアin京たなべ2012

2012/10/11
同志社大学多々羅キャンパスでビジネスフェアin京たなべ2012開催

2012/10/11
同志社大学多々羅キャンパスでビジネスフェアin京たなべ2012開催

同志社大学多々羅キャンパスで開催されたビジネスフェアin京たなべ2012に展示出品(ポスター)しました。

ポスターを見る(PDF:897KB)

第17回分子線エピタキシー国際会議 MBE2012

2012年9月23日~28日
奈良にてポスター発表をしました

2012年9月23日~28日
奈良にてポスター発表をしました

分子線エピタキシー国際会議2012(9月23日~28日:奈良)にポスター発表をしました。http://mbe2012.jp/
研究所の名前に使っている界面反応成長(IRE: Interface reaction epitaxy))を利用した,Siと窒素原子NのIRE による単結晶薄膜β-Si3N4およびその結晶中のNと照射Al原子のよるIREを利用したAlN成長を報告した。この2つの層を合わせてDouble buffer layer (DBL : ダブルバッファ層)と呼んでいる。
MBE2012参加者は25カ国から461名(展示と同伴者を含む)日本からは237名の参加。 京田辺市HP ISGN4

MBE ポスターを見る(PDF:3,352KB) MBE Abstractを見る(PDF:279KB)

第4回3族窒化物結晶成長国際シンポジウム

2012年7月16日~19日
ロシア、サンクトペテルブルグにて

2012年7月16日~19日
ロシア、サンクトペテルブルグにて

第4回3族窒化物結晶成長国際シンポジウム(ISGN4 7月16日~19日:ロシア、サンクトペテルブルグ)に参加ポスター発表しProceedings論文提出。伊丹、羽田、パリ経由でサンクトペテルブルグへ。帰路イギリスを訪問
京田辺市の京たなべの逸品販路開拓支援事業補助金交付事業の補助を受けて、京たなべ逸品の展示を会場で行った。

ISGN4ポスターを見る(PDF:315KB)

共同研究論文

2012: CrystEngComm, 2012, 14, 5572?5578
Spray drying mass-production route for Mg-doped LiNbO3 (Mg:LN) polycrystalline powder based on a wet-chemical method

2012: CrystEngComm, 2012, 14, 5572?5578
Spray drying mass-production route for Mg-doped LiNbO3 (Mg:LN) polycrystalline powder based on a wet-chemical method

Qingbo Liu,a Dehui Sun,a Tao Yan,a Feifei Zheng,b Yunhua Sang,a Hong Liu,*a Jiyang Wanga
and Tadashi Ohachic
aState Key Laboratory of Crystal Materials, Shandong University, Shandanan Road, Jinan, 250100, China bYuanhong Technical Materials Ltd., Jining, China
cDepartment of Electrical Engineering, Doshisha University, Kyotanabe, Kyoto 610-0321, Japan

A mass production route for Mg-doped LiNbO3 (Mg:LN) polycrystalline powder was proposed based on a wet-chemical method/spray drying process. A stable homogenous precursor solution was prepared by dissolving commercial Nb(OH)5, Li2CO3 and MgO, and was stabilized with citric acid (CA) as a chelating agent. Spherical Mg:LN precursor powder can be obtained by a spray-drying method, and spherical mono-phase perovskite Mg:LN polycrystalline powder with uniform size was obtained by calcining the precursor powder at relatively low temperature. Thermogravimetry? differential thermal analysis (TG?DTA), X-ray diffraction (XRD), infrared spectroscopy and scanning electron microscopy (SEM) were used to characterize the precursor and product powder. The as-obtained Mg:LN powder was used for Mg:LN single-crystal growth. The obtained Mg:LN single crystal possesses both high optical homogeneity and ingredient uniformity. This mass production route for preparation of Mg:LN powder provides a solution to the problem of defects in Mg:LN single crystals caused by nonhomogeneity of magnesium distribution.

論文を読む(PDF:645KB)

2012: CrystEngComm, 2012, 14, 1783?1789
Ammonium sulfate regulation of morphology of Nd:Y2O3 precursor via urea precipitation method and its effect on the sintering properties of Nd:Y2O3 nanopowders

2012: CrystEngComm, 2012, 14, 1783?1789
Ammonium sulfate regulation of morphology of Nd:Y2O3 precursor via urea precipitation method and its effect on the sintering properties of Nd:Y2O3 nanopowders

Haiming Qin,a Hong Liu,*a Yuanhua Sang,a Yaohui Lv,b Xiaolin Zhang,a Yuanyuan Zhang,a Tadashi Ohachicand Jiyang Wang*a
aState Key Laboratory of Crystal Materials, Shandong University, Jinan,250100, China. E-mail: hongliu@sdu.edu.cn; Jywang@sdu.edu.cn; Fax:+86-531-88362807; Tel: +86-531-88362807bSchool of Materials Science and Engineering, Anhui University ofTechnology, Maanshan, 241002, ChinacDepartment of Electrical Engineering, Doshisha University, Kyotanabe,Kyoto, 610-0321, Japan

Ammonium sulfate has been widely used as a control agent in the preparation of yttrium-aluminiumgarnet(YAG) transparent ceramics, however, research of its application in the preparation intransparent ceramic yttria has not been intensively studied. Neodymium?doped yttria (Nd:Y2O3)nanopowders with controlled morphology and size were synthesized via a urea precipitation methodusing ammonium sulfate as the additive. The effect of ammonium sulfate was intensively studiedthroughout the preparation process. Morphology of precursors was found to be evidently affected bythe [(NH4)2SO4]/[Nd:Y2O3] ratio (measured by weight). Uniform spheres of Nd:Y2O3 precursor wereobtained without the addition of ammonium sulfate. With increasing amounts of ammonium sulfateadded, the scale of the Nd:Y2O3 precursors diminished which results in the aggregation of the Nd:Y2O3precursor. Aggregates of coral like particles after precipitation and uniform well dispersed particlesafter calcinations were obtained as the dosage of ammonium sulfate reached 20 wt%. It was consideredto be the optimum state for the preparation of highly sinterable Nd:Y2O3 nanopowders. Ammoniumsulfate was proved to be a regulator that could mediate the nucleation and growth of the precursor aswell as its decomposition behaviour. Results of this paper can contribute to the controllable synthesis oftransparent ceramic yttria.

論文を読む(PDF:704KB)

プロジェクト報告 2006~2010年度

報告8(2010年度)
窒素原子フラックス計測とrfプラズマによるSi(111)上 β-Si3N4の成長(3)

報告8(2010年度)
窒素原子フラックス計測とrfプラズマによるSi(111)上 β-Si3N4の成長(3)

最終年度のまとめとして、窒素原子間接照射法によるβ-Si3N4DBLの成長,β-Si3N4上のIRE-AlNをテンプレートとしたALEの一つとして活性度変調マイグレーションエンハンスト成長(Activation modulation migration enhanced epitaxy)法を報告すると共にPA-MBE法に必要なrfプラズマによる窒素原子発生と計測,窒素原子フラックス計測方に直接照射のフラックスを計測可能な新しい多層平行メッシュ電極原子束プローブ( Multiple parallel mesh electrodes atom flux probe : M-PME atom flux probe ) を報告する。

論文を読む(PDF:1,699KB)

報告7(2010年度)
3族窒化物PA-MBE成長用AlN/β-Si3N4ダブルバッファ層の界面反応エピタキシー成長(2)

報告7(2010年度)
3族窒化物PA-MBE成長用AlN/β-Si3N4ダブルバッファ層の界面反応エピタキシー成長(2)

Si基板上にAlN単結晶成長膜を有するDBLの成長法のまとめを行い,六方晶3族窒化物の(0001)膜の極性が出発下地の極性によることと,過剰なAl照射による表面の擬似液体層(Quasi Liquid Layer: QLL)の存在でAl極性がN極性に反転することを報告する.8x8再構成を持つ-Si3N4上でAlを1.8ML照射した場合AlNの表面再構成層は2x6構造を示しAlNの極性はAl極性を示していることがわかる.それに対し,20ML堆積した場合表面のRHEED像は3x3構造を示しN極性となっていることがわかる.これは20MLのAlのQLLがDBL上を覆い,その上に成長させたAlNはQLL上で成長するためにDBL上成長の極性とは異なる極性をとるためである。また,DBLの界面荒さと,GaN/AlN/DBL/Si(111)構造のGaN膜中の貫通転位および各界面のラフネスの関係を調べ,DBLの平坦性が重要であることを示した。

論文を読む(PDF:1,735KB)

報告6(2009年度)
窒素原子フラックス計測とrfプラズマによるSi(111)上 β-Si3N4の成長(2)

報告6(2009年度)
窒素原子フラックス計測とrfプラズマによるSi(111)上 β-Si3N4の成長(2)

窒素原子を間接に照射する吸着N原子の発生方法と測定方法,それを利用したSiの表面処理,ダブルバッファーテンプレート用β-Si3N4のIREによる作製への応用を報告する。間接照射の場合窒素原子のフラックス測定を目的として平行平板電極を用い負電位の2電極間に流れる電流をりようする方式を示す。

論文を読む(PDF:2,252KB)

報告5(2009年度)
3族窒化物PA-MBE成長用AlNl/β-Si3N4ダブルバッファ層の界面反応エピタキシー成長

報告5(2009年度)
3族窒化物PA-MBE成長用AlNl/β-Si3N4ダブルバッファ層の界面反応エピタキシー成長

この研究は前回での報告[3族窒化物RF-MBE成長用AlNテンプレートのAl/β-Si3N4界面反応成長に引き続き, 界面反応エピタキシー(Interface Reaction Epitaxy : IRE)法を用いてSi上にAlNl/β-Si3N4ダブルバッファ層を形成する方法の最適化を行うため,AlN形成量の定量化を行い, IRE-AlN上のGaN成長の特徴を示したものである. 今回の報告では, X線光電子分光(X-ray Photoelectron Spectroscopy:XPS)を用いてRF放電で作製したβ-Si3N4薄膜の厚みを測定するとともに, 界面反応AlNの形成量変化させる要因であるAl照射条件および窒化条件を変化させAlNが最大形成する条件を探るとともに, 界面反応AlNの上にGaN/AlN構造を作製し, GaNの極性および表面平坦化の方法について示した。

論文を読む(PDF:1,005KB)

報告4(2008年度)
窒素原子フラックス計測とRFプラズマによるSi(111)上 β-Si3N4の成長

報告4(2008年度)
窒素原子フラックス計測とRFプラズマによるSi(111)上 β-Si3N4の成長

第3年目2008年度として,界面反応に利用される放電により生成した窒素原子フラックスの制御に必要な、窒素原子の自己電離現象を利用した窒素原子フラックス計測法の改良とSi 表面での窒化反応による界面反応エピタキシーによるβ-Si3N4成長に必要なSi表面清浄化法の開発を報告する.更にヘテロエピタキシャル成長に必要なSi表面の平坦化と清浄化に対する検討を行い,今までの多くに研究報告を調べることにより,続くAlNテンプレート成長に必要なβ-Si3N4作製に方向付けを示す。

論文を読む(PDF:726KB)

報告3(2008年度)
3族窒化物RF-MBE成長用AlNテンプレートのAl/β-Si3N4界面反応成長

報告3(2008年度)
3族窒化物RF-MBE成長用AlNテンプレートのAl/β-Si3N4界面反応成長

本報告では第1報で報告した窒素の活性種とSi基板表面で反応しSi上の界面反応エピタキシャル窒化シリコン単結晶β-Si3N4を基板として,その表面にAl原子を1-2ML照射してβ-Si3N4中の窒素原子とAl原子の固相反応である界面反応エピタキシャル法でAlN結晶を成長させる方法を提案する。さらにこの反応性エピタキシーによって作られたAlNの上にMBE法もしくはAM-MEE法でAlN膜をエピタキシャル成長させる。Si表面の窒化により形成したβ-Si3N4中の窒素原子と表面Al原子が反応しβ-Si3N4表面上にAlNが形成され,AlNの表面形状が下地のβ-Si3N4成長の際に使用する窒素活性種,照射方法,窒化時間およびSi表面再構成に依存いるということを示す。

論文を読む(PDF:835KB)

報告2(2007年度)
活性度変調マイグレーションエンハンストRF-MBE成長法によるSi基板上のAlN,GaNヘテロエピタキシャル成長

報告2(2007年度)
活性度変調マイグレーションエンハンストRF-MBE成長法によるSi基板上のAlN,GaNヘテロエピタキシャル成長

活性度変調マイグレーションエンハンストエピタキシー: AM-MEE (Activity modulation migration enhanced epitaxy)を提案し,それを利用したSi基板上への六方晶AlNとGaNエピタキシャル成長を研究した結果について報告。中性窒素原子の自己電離を用いたN原子フラックスを電流計測で可能にし,原子電極を開発試作した。窒化膜形成後に約2MLのAl照射によりAl極性の 2H-AlN成長を報告しAl照射量により極性制御が出来ることを示した。HVPE法によるAlN成長のテンプレートとして利用しピットやそれと関連して生じる表面の規則的なひび割れが昇温降温過程に関係していることが明らかになった。

論文を読む(PDF:1,575KB)

報告1(2006年度)
シリコン上への3族窒化物系半導体ナノヘテロ界面量子井戸構造の結晶成長と物性評価

報告1(2006年度)
シリコン上への3族窒化物系半導体ナノヘテロ界面量子井戸構造の結晶成長と物性評価

「界面現象研究センター」研究の1年目の報告であり、それまでの研究で取り組んだSI(111)、Si(100)上のSiCバッファ層による六方晶及び立方晶GaNエピタキシャル成長とSi(111)上のγAlバッファ層からAlN成長を報告している。高周波放電による原子状窒素生成に関した誘導結合放電の2つのモードの特徴を理解する研究として、窒素分子励起モードの弱い放電LBと窒素分子解離モードの明るい放電HBの切換により,励起分子照射と原子と励起原子及び励起分子照射の切換を可能にするMC-MEE結晶成長法を開発し、SiCに替わる新しいテンプレートとして窒素放電によるSi3N4テンプレートを提案している。

論文を読む(PDF:991KB)

Published academic papers

2013 : P hys. Status Solidi C 10, No. 3, 429?432 (2013)
Tadashi Ohachi, Yuka Yamamoto, Osamu Ariyada, Yuuki Sato, Sinzo Yoshikado, and Motoi Wada

2013 : P hys. Status Solidi C 10, No. 3, 429?432 (2013)
Tadashi Ohachi, Yuka Yamamoto, Osamu Ariyada, Yuuki Sato, Sinzo Yoshikado, and Motoi Wada

Activity modulation MEE growth of group III nitrides on Si(111) using PA-MBE

As a demonstration of the activity modulation migration enhanced epitaxy (AM-MEE) heteroepitaxial 2H-AlN thin films of 53.8 nm and 171.3 nm thickness on Si(111) on a double buffer layer (DBL) have been grown by the AM-MEE of plasma assisted molecular beam epitaxy (PA-MBE) method. It is a droplet free growth and an atomic layer epitaxy (ALE). The influence of the DBL, which was formed in a MBE chamber before the AM-MEE growth of 2H-AlN thin films on Si(111), was studied to improve the crystallinity of AlN films. For the growth of high quality 2H-AlN on Si(111), the optimization of growth of the DBL. The interface roughness of the DBL as a layer between two layers of AlN and Si, AlN/DBL/Si was characterized by grazing incidence Xray reflectivity (GIXR) and the surfaces were observed by AFM. Full width at half maximum (FWHM) of ω /2θ for 53.8 nm and 171.3 nm thickness AlN (0002) films were 12.1 arcmin and 7.1 arcmin, respectively. AFM images showed droplet free growth after the AM-MEE and importance of the preparation of initial clean Si surface. Unifrom formation of DBL on a large size wafer of Si was available to use indirect exposure of N radical atoms. By increasing the thickness of the AlN the crystallinity was improved but the surface roughness of AlN did not depend on the thickness of the AlN films obtained by fitting results of GIXR curves.

論文を読む(PDF:440KB)

2011: P hys. Status Solidi C 8, No. 5, 1552?1555 (2011)
Epitaxial growth of β-Si3N4 by the nitridation of Si with adsorbed N atoms for interface reaction epitaxy of double buffer AlN(0001)/ β-Si3N4/Si(111)

2011: P hys. Status Solidi C 8, No. 5, 1552?1555 (2011)
Epitaxial growth of β-Si3N4 by the nitridation of Si with adsorbed N atoms for interface reaction epitaxy of double buffer AlN(0001)/ β-Si3N4/Si(111)

A fabrication process of an interface reaction epitaxy (IRE) β-Si3N4 and an IRE AlN were investigated to produce a double buffer layer (DBL) of AlN(0001)/β- Si3N4/Si(111) for the growth of group III nitrides films on Si. The β-Si3N4 was formed by using adsorbed (ADS) nitrogen atoms irradiated indirectly from a rf-plasma cell. Two surface structures of the β-Si3N4, which were “8 x 8” and “8/3 x 8/3” reconstructions, were fabricated by changing the nitrogen irradiation conditions; complete and incomplete nitridation of Si surface and successive heat treatment up to 875 oC formed the “8 x 8” and “8/3 x 8/3” structures, respectively. IRE AlN was grown by 1 monolayer of Al deposition on the β-Si3N4 and successive annealing at 875 oC. Al and N polarity DBLs were grown on the “8 x 8” and “8/3 x 8/3” structures, respectively. These results indicated that the polarity of DBL could be controlled by the surface reconstruction of β-Si3N4.

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2011: P hys. Status Solidi C 8, No. 5, 1491?1494 (2011)
In situ measurement of adsorbed nitrogen atoms for PA-MBE growth of group III nitrides on Si

2011: P hys. Status Solidi C 8, No. 5, 1491?1494 (2011)
In situ measurement of adsorbed nitrogen atoms for PA-MBE growth of group III nitrides on Si

An atom probe of two parallel electrodes is proposed to monitor adsorbed (ADS) nitrogen atoms in situ during growth of β- Si3N4 using indirect exposure of effusing active nitrogen beam from the radio frequency induction coupled plasma cell. The β- Si3N4 film is a component of a double buffer layer (DBL) AlN(0001)/β-Si3N4/Si(111) to grow high quality the group III nitrides and their alloys on Si. Atom current between the parallel electrodes corresponds to flux of the ADS nitrogen atoms on the inside surface at the atom potential, VA. The ADS atom current received influence of wall and shutter of the cell, because adsorption of nitrogen atom depended wall condition such as temperature and the concentration of adatoms on the wall.

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2011: Journal of Crystal Growth 318 (2011) 474?478
Interface roughness of double buffer layer of GaN film grown on Si(111) substrate using GIXR analysis

2011: Journal of Crystal Growth 318 (2011) 474?478
Interface roughness of double buffer layer of GaN film grown on Si(111) substrate using GIXR analysis

A double buffer layer (DBL), interface reaction epitaxy (IRE) AlN/b-Si3N4/Si, grown by an IRE of b-Si3N4 and AlN films on Si, was fabricated to improve the crystalline quality of successively grown 30 nm GaN on a 30 nm AlN buffer layer using plasma-assisted molecular beam epitaxy (PA-MBE). The DBL was first prepared by surface nitridation of Si and successively prepared by IRE between the deposited Al and N atoms in b-Si3N4. Both the AlN buffer layer on the DBL and GaN filmon the AlN buffer layer were grown by activity-modulation migration enhanced epitaxy (AM-MEE). Hetero epitaxial grown films of GaN(30 nm)/AlN buffer(30 nm)/DBL/Si(1 1 1) were prepared for analysis using a three layer model of grazing incidence-angle X-ray reflectivity (GIXR), which consisted of three layers of GaN, AlN buffer and Si and of the three interfaces of the GaN surface, GaN/AlN buffer and AlN buffer/DBL/Si. The nitridation temperature dependence of the interface roughness of the DBL was measured to be 0.5 and 0.6 nm, for nitridation temperatures of 780 and 830 1C, respectively. The full width at halfmaximum (FWHM) of rocking curve GaN(0 0 0 2) measured by X-ray diffraction (XRD) for nitridation temperatures of 780 and 830 1C were 58.2 and 55.2 arcmin, respectively.

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2011: Journal of Crystal Growth 318 (2011) 468?473
Control of active nitrogen species used for PA-MBE growth of group III nitrides on Si

2011: Journal of Crystal Growth 318 (2011) 468?473
Control of active nitrogen species used for PA-MBE growth of group III nitrides on Si

A new spiral parallel mesh electrode (PME) is presented to control active nitrogen species in plasmaassisted molecular beam epitaxial (PA-MBE) growth of group III nitrides and their alloys. Direct flux of active nitrogen from radio frequency inductive coupled plasma (rf-ICP) discharge was able to be measured using a mesh electrode for filtering charge particles and electron emission due to the selfionization of nitrogen atoms on a negatively biased electrode. In situ measurement of direct nitrogen atom fluxes using the spiralPME during PA-MBE growth of GaN and AlN on Si substrates is investigated. A linear rf power dependence of direct flux of active species on atoms such as nitrogen (N+Nn), where N and Nn were ground and excited atoms, respectively, from a rf-ICP was confirmed by the spiral PME. An indirect flux of nitrogen adsorbed (ADS) atoms (N+Nn) during discharge was also monitored by the spiral PME and received influence of the wall surface of the growth chamber. ADS nitrogen atoms are able to be used for nitridation of Si surface to grow a double buffer layer (DBL) AlN/b-Si3N4/Si.

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2011: Japanese Journal of Applied Physics 50 (2011) 01AE01
Improvement of Plasma-Assisted Molecular Beam Epitaxial Growth of Group III Nitrides on Si Controlling Radio Frequency Discharge Modes and Irradiation of Nitrogen Flux

2011: Japanese Journal of Applied Physics 50 (2011) 01AE01
Improvement of Plasma-Assisted Molecular Beam Epitaxial Growth of Group III Nitrides on Si Controlling Radio Frequency Discharge Modes and Irradiation of Nitrogen Flux

A radio frequency inductively coupled plasma (rf-ICP) nitrogen discharge was investigated to improve group III nitride growth on Si substrates. Two modes of the rf-ICP discharge, low brightness (LB) and high brightness (HB) discharges, were successfully controlled through mode transition. Direct irradiation and indirect irradiation of nitrogen atoms were applied for the growth of group III nitrides. As an application of indirect irradiation of nitrogen atoms, the growth of _-Si3N4 using interface reaction epitaxy (IRE) was studied. As applications of direct irradiation of nitrogen atoms, activity modulation migration-enhanced epitaxy (AM-MEE) and plasma-assisted molecular beam epitaxy (PA-MBE), which are atomic layer epitaxy (ALE) methods, are demonstrated. These growth systems operate to realize a single-growth process from a Si substrate to an AlN or GaN epitaxial layer, i.e., through preparation of a double buffer (DBL) layer of AlN/_-Si3N4/Si after the growth of IRE _-Si3N4 and IRE AlN. The electron emission due to the self-ionization of nitrogen atoms on a negatively biased electrode is demonstrated to measure in situ direct and indirect nitrogen atom fluxes during the growth. # 2011 The Japan Society of Applied Physics

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2009: Journal of Crystal Growth 311 (2009) 2987?2991
Measurement of nitrogen atomic flux for RF-MBE growth of GaN and AlN on Si substrates

2009: Journal of Crystal Growth 311 (2009) 2987?2991
Measurement of nitrogen atomic flux for RF-MBE growth of GaN and AlN on Si substrates

Production and measurement of active nitrogen atoms (N+N*), which consist of ground state nitrogen atoms N and excited state nitrogen atoms N*, in an inductively coupled radio frequency discharge for the growth of group III nitrides and their alloys using a molecular beam epitaxy (MBE) were studied. Two discharge modes of the low brightness (LB) and the high brightness (HB) used in this study to produce excited nitrogen molecules (N2*) and dissociated active nitrogen atoms (N+N*). The flux of (N+N*) was measured by a Langumuir-like electrode due to the self-ionization of adsorbed (N+N*) on a negatively biased electrode. The self-ionization, which emits electrons from (N+N*), forms an atom current and is confirmed using different electrodes such as Pt and CuBe and different electrode area. The atom current was calibrated by the grown GaN thickness in a VG80H MBE machine. The calibrated flux of (N+N*) per atom current in the VG80H machine is 5.5_10_4ML/s/nA, where ML is monolayer. The atom current is useful to monitor the flux of chemically active nitrogen atoms N+N* for growth of group III nitrides and their alloys. Activity modulation migration enhanced epitaxial growth (AM-MEE) was demonstrated as an application of the measurement of atom current for the growth of the group III nitrides.

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2009: Journal of Crystal Growth 311 (2009)
Nitridation of Si(111) for growth of 2H-AlN(0 0 01)/b-Si3N4 /Si(111) structure

2009: Journal of Crystal Growth 311 (2009)
Nitridation of Si(111) for growth of 2H-AlN(0 0 01)/b-Si3N4 /Si(111) structure

Using various nitrogen active species with different chemical and physical activities, nitridation of Si(111) was studied for the growth of group III nitrides and their alloys using a radio frequency molecular beam epitaxy. Nitrogen inductive coupling discharge produced dissociated active nitrogen atoms (N+N*), which are ground state atom N and excited atom N*, excited molecules N!2, and molecule ions N2 + . The surface morphology of b-Si3N4 was affected by the kind of nitrogen species. Flat surface was obtained by using only (N+N*) with slow nitridation of 0.02 ML/s. When nitridation was performed by (N+N*) and N!2, many steps and many 10nm height spikes were observed. It was essential for nitridation to eliminate nitrogen ions (N2 + ). In comparison with this result, when N!2 were used, the island size of b-Si3N4 became bigger without detachment from upper terrace. This island size affected successive surface structure of AlN. It is a key technique to achieve flat surface of b-Si3N4 that N+N* flux was used for nitridation. The growth of 2H-AlN(0 0 01)/b-Si3N4/Si(111) structure was also performed. RMS value of AlN grown on b-Si3N4 which was formed by (N+N*) became 0.88 nm.

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2006: phys. stat. sol. (c) 3, No. 6, 1404?1407 (2006)
Radio-frequency MBE growth of cubic GaN on 3C-SiC(001)/Si(001) template

2006: phys. stat. sol. (c) 3, No. 6, 1404?1407 (2006)
Radio-frequency MBE growth of cubic GaN on 3C-SiC(001)/Si(001) template

A 3C-SiC(001) was formed by coincidence site lattice matching on Si(001) through carbonization using acetylene (C2H2) supplied by a jet nozzle. The 3C-SiC serves as a cubic template for the MBE growth of c-GaN on Si substrates. The Si substrate with lattice constant of aSi = 0.544 nm was covered with strained 3C-SiC whose lattice constant a3C-SiC/Si = 0.445 nm expanded from that of the bulk 3C-SiC crystal (0.438 nm). Better quality cubic phase GaN film was grown on the strained 3C-SiC template layer when the Ga/N flux ratio approached unity of Ga rich side. The proportion of the cubic phase in the GaN layer was calculated to be 94.7% from the integrated intensity ratio of the X-ray diffraction peaks of c-GaN(002) and h-GaN(10-11). The FWHM of the (002) diffraction peak for the 544 nm-thick c-GaN was 13.2 arcmin. A precise RHEED analysis also indicated that the c-GaN had (2x2) surface reconstruction structure.

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2006: phys. stat. sol. (c) 3, No. 6, 1383?1387 (2006)
Radio-frequency MBE growth of cubic GaN on BP(001)/Si(001) hetero-structure

2006: phys. stat. sol. (c) 3, No. 6, 1383?1387 (2006)
Radio-frequency MBE growth of cubic GaN on BP(001)/Si(001) hetero-structure

Zincblende gallium nitride (c-GaN) was grown on zincblende boron monophosphide (BP)/silicon (001) using radio-frequency plasma-assisted molecular-beam epitaxy (RF-MBE). In spite of near perfect latticematch coordination between c-GaN and BP, the initial nucleation of c-GaN was 3D island formation due to imperfect wetting. Using cross-sectional electron backscatter diffraction pattern (x-EBSD), it was found that dislocations were eliminated with an increase of epilayer thickness of c-GaN, and finally 99.4% c-GaN (001) was achieved. The (2x2) and (4x1) reconstructions of the surface of almost pure c- GaN (001) were confirmed by reflection high-energy electron diffraction (RHEED) under arseniccontamination free conditions.

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2006: Journal of Crystal Growth 292 (2006) 221?226
Role of excited nitrogen species in the growth of GaN by RF?MBE

2006: Journal of Crystal Growth 292 (2006) 221?226
Role of excited nitrogen species in the growth of GaN by RF?MBE

Optical emission spectroscopy (OES) was used with the combinatorial growth method to investigate the behavior of excited nitrogen species in the growth of gallium nitride (GaN) using radio-frequency molecular beam epitaxy (RF?MBE). To determine the amounts of each excited nitrogen species in the nitrogen plasma, the integrated OES intensity (IOI) method was proposed. The IOI measurements revealed the following: more nitrogen ions .N.2 . were produced at the lower inlet pressure of nitrogen, the productivity of nitrogen atoms (N) and excited nitrogen atoms (N*) had an optimum value at some inlet pressure, whereas the productivity of excited nitrogen molecules .N$2 . saturated as the inlet pressure increased. The combination of the IOI measurement and the combinatorial growth of GaN showed that not only N and N*, but also the long-lifetime A3S.u state of N$2 contributed to GaN growth using RF?MBE.

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2006: J. Rare Earths, 24 (2006)1.
Growth of GaN/AlxGa1-xN (x=0.65) superlattices on Si(111) substrates using RF-MBE

2006: J. Rare Earths, 24 (2006)1.
Growth of GaN/AlxGa1-xN (x=0.65) superlattices on Si(111) substrates using RF-MBE

Superlattices with varying GaN well widths (2, 3, 6, 9 nm) and fixed AlGaN barrier (8nm) with high Al-content (x=0.65) were grown. Streaky RHEED patterns indicated 2D growth mode for the superlattices. XRD measurements showed multiple satellite peaks corresponding to uniform periodicity of the GaN/AlGaN pairs. The AlGaN barrier XRD peak also shifted with increasing well widths, while the GaN XRD peak was nominally unchanged. Room temperature photoluminescence experiments revealed peak emissions at energies lower than the bulk GaN energy gap. The large red shift with respect to the bulk gap is attributed to significant Stark effect for wide multiple quantum wells.

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2005: Journal of Crystal Growth 275 (2005) e1215?e1221
3C-SiC/Si template growth and atomic layer epitaxy of cubic GaN by RF-MBE

2005: Journal of Crystal Growth 275 (2005) e1215?e1221
3C-SiC/Si template growth and atomic layer epitaxy of cubic GaN by RF-MBE

Growth of 2 in cubic gallium nitride (c-GaN) film on a cubic silicon carbide on Si template (3C-SiC/Si) using Si (0 0 1) and Si(1 1 1) substrates was performed by usinga radio frequency molecular beam epitaxy (RF-MBE) system, which was equipped with a jet nozzle. The 3C-SiC/Si template was prepared usingalternatingexposure of acetylene .C2H2. gas introduced by the jet nozzle under ultra high vacuum and Si molecular beam from a Si effusion cell. Very smooth 3C-SiC/Si templates with RMS roughness by atomic force microscopy of about 0.2?0.4nm were grown here. Good crystal quality of low-temperature buffer (LTB) layer was obtained on a good 3C-SiC/Si template and confirmed through the observation of RHEED pattern. A grown c-GaN film’s X-ray diffraction full-width at half-maximum of (0 0 2) peak was 13.2 arcmin (2y) for a 544 nm-thick film. c-GaN was also grown using an atomic layer epitaxy (ALE) method. The ALE method proved to be necessary for a uniform and homogeneous atomic nitrogen flux under slightly Ga excess condition to grow the uniform c-GaN using rf-MBE.

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2005: Journal of Crystal Growth 275 (2005) e1197?e1202
Control of nitrogen flux for growth of cubic GaNon 3C-SiC/Si by RF-MBE

2005: Journal of Crystal Growth 275 (2005) e1197?e1202
Control of nitrogen flux for growth of cubic GaNon 3C-SiC/Si by RF-MBE

The enhancement of the production rate of nitrogen radical from a radio frequency (RF) discharge plasma is reported through the application of a DC magnetic field under RF-ECR (electron cyclotron resonance of RF) condition. High efficiency of the nitrogen radical production was realized by an optimum magnetic field for the resonance of about 0.5mT for the electron energy of 2 eV for the 13.56-MHz discharge. The effect of controlling the divergence of the nitrogen radical flux by changing the orifice dimension was studied by measuring the color change of interference due to the film thickness. The aspect ratio of the orifice hole and the distribution of hole position determined the flux diversity. Combinatorial methodology, which realizes various III/V flux ratio without substrate rotation due to non-uniform flux, was used to study the effect of the III/V flux ratio to poly-type formation by photoluminescence. The cubic phase was grown under a stoichiometric condition of slightly Ga-rich side, with an III/V ratio of about one.

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2003: phys. stat. sol. (c) 0, No. 7, 2589?2592 (2003)
Direct growth of cubic AlN and GaN on Si (001) with plasma-assisted MBE

2003: phys. stat. sol. (c) 0, No. 7, 2589?2592 (2003)
Direct growth of cubic AlN and GaN on Si (001) with plasma-assisted MBE

Highly lattice mismatched (HM2) heteroepitaxial growth of cubic zincblende c-AlN and c-GaN on Si(001) was performed by MBE using plasma excited nitrogen sources without using a low temperature buffer layer. The early stage of the direct nucleation of AlN and GaN on a Si substrate using microwave and radio frequency plasma-assisted MBE was studied. The islands of a zincblende structured material (c-SiNx [a = 0.43 nm]), effectively worked as a seed for successive coherent growth of c-AlN and c-GaN oriented 〈001〉. The growth of c-AlN and c-GaN was analyzed by reflection high energy electron diffraction, X-ray diffraction, and photoluminescence.

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