Evaluation and re-growth of p-GaN on nano-patterned GaN on sapphire substrate

Physica Status Solidi (C) Current Topics in Solid State Physics


AlGaN epitaxial lateral overgrowth on Ti-evaporated GaN/sapphire substrate


GaN- and AlGaN-based UV-LEDs on Sapphire by Metalorganic Chemical Vapor Deposition


Blue light emitting diode fabricated on a-plane GaN film over r-sapphire substrate and on a-plane bulk GaN substrate


Growth of AlN and GaN by metalorganic chemical vapor deposition on BP synthesized by flux method

BP with the size of 50 μm to 3 mm was synthesized by the Cu flux method. The BP crystals have a zincblend structure, and the lattice constant and the cathodoluminescence peak wavelength were 4.557 Å and 370 nm, respectively. GaN and AlN were grown by metalorganic chemical vapor deposition on BP. It was found that AlN grown at 1150 °C on (100)BP was grown smoothly but that grown on (111)BP had a rough surface. GaN, however, was irregularly grown on both (100) and (111)BP. It was demonstrated that AlN on (100)BP is another candidate as a substrate for a UV-light-emitting diode.

Japanese Journal of Applied Physics, Part 2 (Letters)


Effect of middletemperature intermediate layer on crystal quality of AlGaN grown on sapphire substrates by metal organic chemical vapor deposition


Al0.17Ga0.83N Film Using Middle-Temperature Intermediate Layer Grown on (0001) Sapphire Substrate by Metal-Organic Chemical Vapor Deposition

The reduction of the dislocation density in a high-temperature (HT)-Al0.17Ga0.83N epitaxial layer was achieved by a middle-temperature (MT)-intermediate layer technique, in which the HT and the MT were 1050 and 950 °C, respectively. For one set of the MT-intermediate layer, the structure was 4.5-μm-thick HT-Al0.17Ga0.83N/1-μm-thick MT-intermediate layer/100-nm-thick HT-Al0.17Ga0.83N layer/low-temperature (LT)-GaNP buffer/trenched (0001) sapphire. The full-width at half maximum values of (0002) and ($10ar{1}2$) diffraction peaks of the X-ray diffraction for the Al0.17Ga0.83N epitaxial layer using one set of the MT-intermediate layer were improved to 359 and 486 arcsec compared with 401 and 977 arcsec for the film without the MT-intermediate layer technique, respectively. Transmission electron microscopy result showed that the dislocation density in the Al0.17Ga0.83N film using one set of MT-intermediate layer was reduced from $(1--4)imes 10^{10}$ to $1.7imes 10^{9}$ cm-2. The Al0.17Ga0.83N epitaxial film including two sets of MT-intermediate layers improved the most, showing a dislocation density of $9.3imes 10^{8}$ cm-2.


Al0.17Ga0.83N film with Middle Temperature Intermediate Layer Grown on Trenched Sapphire Substrate by MOCVD


Growth of thich a-plane GaN on r-plane sapphire by direct synthesis method


Inversion domain in AlGaN films grown on patterned sapphire substrate


Effect of GaNP Buffer Layer on AlGaN Epilayers Deposited on (0001) Sapphire Substrates by Metalorganic Chemical Vapor Deposition

AlxGa1-xN ($x eq 0.1$) epilayers grown on (0001) sapphire substrates by low-pressure metalorganic chemical vapor deposition with low-temperature (LT)-GaNP buffer have been characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). It is found that the full width at half maximum (FWHM) values of the GaNP-buffer-based AlxGa1-xN ($x eq 0.1$) epilayers decrease are lower than that of the conventional GaN-buffer-based AlxGa1-xN ($x eq 0.1$) epilayers, but the difference becomes smaller as the Al composition increases. These results could be mainly attributed to a longer diffusion length with the GaNP buffer layer than with the GaN buffer layer.


Effects of V/III flux ratio on AlInGaN/AlGaN quantum wells grown by atmospheric pressure MOCVD


Fabrication of high-output-power AlGaN/GaN-based UV-light-emitting diode using a Ga droplet layer

GaドロップレットをはさみこみLEDの効率が改善した．Gaにより，その回りが歪みがあるようである．その歪みにより効率が改善する．


Bulk GaN growth by direct synthesis method

直接合成法によるバルクGaNの結晶成長を行った．サファイア基板上にMOCVD法により薄膜GaNを成長したものを基板に用いると平坦な表面の厚膜GaNが得られた．サファイア上に直接成長を行うと表面は荒れ結晶性の良くないGaNが成長したが，直接合成法でもバッファ層を導入することにより表面が平坦で結晶性の良い厚膜GaNを成長することに成功した．


Optical properties of bound excitons and biexcitons in GaN

Excitonic optical properties of GaN homoepitaxial layers have been studied by means of magneto-luminescence and time-resolved luminescence spectroscopy. The luminescence lines due to the radiative recombination of excitons bound to neutral donors and acceptors have been measured under magnetic field up to 8T, which was aligned perpendicular and parallel to the hexagonal c-axis. Under the magnetic field aligned perpendicular to the hexagonal c-axis, both the donor- and acceptor-bound-exciton lines clearly split into two components, which originated from the Zeeman splitting. The effective g-factors for both the donor- and acceptor-bound excitons were estimated to be 2.02 and 2.47, respectively. Under the magnetic field aligned parallel to the hexagonal c-axis, slight broadening of the bound-exciton lines was observed and the Zeeman splitting was too small to be detected. On the other hand, the diamagnetic shift for both the donor- and acceptor-bound-exciton luminescence lines was observed under the magnetic field aligned both perpendicular and parallel to the hexagonal c-axis. It was found that the diamagnetic shift of the donor-bound exciton was smaller than that of the acceptor-bound exciton. Furthermore, recombination dynamics of excitonic transitions was measured under high-density excitation. An excitation-density-dependent transition of the dominant radiative recombination process from donor-bound excitons to biexcitons was clearly observed in the temporal behavior. In addition, double-exponential decay of biexciton luminescence was observed, which is one of the characteristics of biexciton luminescence at high excitation densities.


Selective fabrication of InGaN nanostructures by the focused ion beam/metalorganic chemical vapor deposition process

サファイア基板上に成長したGaNをSIでコートし，部分的にFIBで窓を開けることにより選択的にInGaNナノ構造を作製した．ナノ構造はMOCVD法により作製したが，窓を開けた部分にのみInGaN/GaNが成長し，その先端部分に量子細線もしくは量子ドットが形成されていることをSEMやCLによって確認した．


Characterization of RIE etched surface of GaN using methane gas with chlorine plasma

Journal of Vacuum Science & Technology B


Growth of GaN layer by metallorganic vapor deposition system with a novel three-flow reactor


Time-resolved spectroscopy of excitonic luminescence from GaN homoepitaxial layers


Dependence of growth conditions on morphology in lateral epitaxial overgrowth of GaN by sublimation method

昇華法によるGaNの選択横方向成長について表面モホロジーと結晶品質の成長条件依存性を調べた．成長温度が上がるにつれて，選択的に成長したストライプの断面形状が三角形から長方形に変化する様子がSEMにより確認できた．またAFMによる観察の結果，ステップ成長により二次元成長することが示された．


Growth of a GaN layer on a glass substrate by metal organic chemical vapor deposition


Magneto-luminescence spectroscopy of excitonic transitions in homoepitaxial GaN layers

Physica Status Solidi (B) Basic Solid State Physics : PSS


Configuration of Dislocations in Lateral Overgrowth GaN Films

LEO成長されたGaN膜の転位分布と光学特性を,カソードルミネッセンス法およびTEMを用いて議論した.転位分布と光放出分布は密接な関係があり,転位はバンド端発光強度に影響を及ぼすだけでなく黄色発光に著しく影響を及ぼすことを明らかにした.


Reactive ion etching of GaN and AlxGa1-xN using Cl2/CH4/Ar plasma

Japanese Journal of Applied Physics, Part 1 (Regular Papers & Short Notes)


Surface morphology studies on sublimation grown bulk GaN by atomic force microscopy


Lateral overgrowth mechanisms and microstructural characteristics of bulk-like GaN layers grown by sublimation method structures Substrates


Role of Dislocation in InGaN Phase Separation

MOCVD成長されたサファイア上のInGaNの光学特性に対する転位の役割をカソードルミネッセンス法およびAFMを用いて議論した.転位は非発光センターとして振る舞うこと,InGaN中の相分離は混合転位によるスパイラル成長により生じることを示した.

Japanese Journal of Applied Physics, Part 2 (Letters)


Characterization of Bulk GaN Grown by Sublimation Technique

昇華法によりつくられたバルクGaNをX線回折,2次イオン質量分析,ラマン散乱分光および電気的特性実験により評価した.本報告で使用したバルク結晶は高い結晶完全性をもち高い純度をもつものであることを示した.


昇華法によるバルクGaN結晶製造技術およびMOCVD法によるホモエピタキシャル成長技術について検討した.バルク結晶の前処理により,ホモエピタキシャル成長後の表面モフォロジー,光学特性が大きく変化することを示した.


Direct Evidence that Dislocations are Non-radiative Recombination Centers in GaN

平面TEM観察およびカソードルミネッセンス像測定を,n型GaNにおいて同一試料·同一場所に対して行った.カソードルミネッセンス像中の暗点は,TEM像中における転位と1対1で対応することを示した.n型GaN中の正孔の拡散距離を約50nmであると評価した.GaN発光効率は,少数キャリヤの拡散長が転位の間隔よりも短いほど高くなることを実験的に明らかにした.


Surface Pretreatment of Bulk GaN for Homoepitaxial Growth by Metalorganic Chemical Vapor Deposition

昇華法により成長されたバルクGaN上へ,有機金属気相成長法によりホモエピタキシャル成長を行い,バルク表面の前処理効果について検討した.平滑な表面をもち,強いカソードルミネッセンス光を発する試料が,バルク結晶に対して適切な前処理を施すことにより得られた.このカソードルミネッセンス光は,サファイア基板上へ成長させたGaN膜から得られるものよりも強い.また,ホモエピタキシャル膜の転位密度は,適切な前処理により,著しく減少する事を示した.


Growth of GaN by Sublimation Technique and Homoepitaxial Growth by MOCVD

昇華法によるバルクGaNおよび有機金属気相成長法によるホモエピタキシャル成長について報告している.昇華法における原料粉は,多種類のガリウム,窒素および水素化物から構成される化合物であることを示した.また,有機金属気相成長法におえる核発生制御手法について検討した.六角形柱状結晶が選択的に形成され,本手法がデバイスプロセスに応用できることを示した.

Material Research Society Symposium Proc.


Transmission Electron Microscopy of Sublimation-Grown GaN Single Crystal and GaN Homoepitaxial Film

昇華法で作製したGaN単結晶上にGaN膜をMOCVD法でホモエピ成長させた．FIB法により加工して電子線が透過する部分を壁状に加工し，結晶内の転位をTEMにより観察した．また，この観察結果に基づき，GaN単結晶内の転位密度を推定した．


Radioimmunoreactive plasma bradykinin levels and histological changes during the course of cerulein-induced pancreatitis in rats.

The plasma bradykinin (BK) and serum amylase levels and histological changes in rats during the course of acute pancreatitis induced by a large dose of cerulein were examined. Animals were given four intraperitoneal injections of 20 micrograms/kg body wt of cerulein at hourly intervals. The plasma concentration of BK-like immunoreactivity (BK-LI), measured by a highly sensitive and specific radioimmunoassay established in this study, was found to reach a peak 6 h after the first injection of cerulein and then to remain elevated. On the other hand, the serum amylase and the histological alterations (i.e., interstitial edema, vacuolization, and inflammatory infiltration) were maximal 9 h after the first injection and returned to nearly normal after 24 h. These observations suggest that the BK generation is indicative of the participation of the kallikrein-kinin system in the pathophysiological change and that the plasma BK-LI level is a good marker of cellular damage and inflammation within the pancreas during the course of acute pancreatitis.


Self-Separation of Sublimation-Grown AlN with AlSiN Buffer Layer

AlN was grown by a sublimation method on 6H-SiC. We found the grown AlN layer is easily separated from the substrate when Si powder is added to the AlN source powder. The formation of AlSiN layer with the Si content of 15% at the AlN/6H-SiC interface was confirmed by energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). This AlSiN layer causes the separation of AlN.


Growth and Characteristics of GaN Film on Thin AlN/(0001) Sapphire Template Layer via Direct Reaction of Gallium and Ammonia

With the advantages of low cost, simplicity, and scalability, a direct reaction using gallium (Ga) and ammonia (NH3) has been employed to deposit GaN film on a (0001) sapphire substrate. We find that only GaN crystallites with diameters in the range of 0.4-5 μm are sparsely deposited on a bare (0001) sapphire substrate. To increase the density of the GaN nucleation site and thus form continuous GaN film, a 50-nm-thick AlN layer [grown on the (0001) sapphire substrate by metalorganic chemical vapor deposition (MOCVD) at 1150 °C in a pulsed manner] is used as a template layer. Plan-view scanning electron microscopy (SEM) and cross-sectional SEM experimental results show that the GaN film has a specular smooth surface and that the film thickness is about 10 μm after 1 h deposition. X-ray diffraction (XRD) and cathodoluminescence (CL) experimental results indicate that the formed GaN film is of single crystals with a hexagonal structure. The full widths at half-maximum (FWHM) of the (002) and (102) X-ray rocking curves are 420 and 556 arcsec, respectively. Our experimental results demonstrate that the growth of high-quality and thick GaN film via a direct reaction is possible.

Japanese Journal of Applied Physics, Part 2 (Letters)


Effect of Oxygen on the Activation of Mg Acceptor in GaN Epilayers Grown by Metalorganic Chemical Vapor Deposition

Mgドープp形GaNの活性化アニール中に雰囲気の窒素に酸素を混ぜることで，p形GaNのホール密度などの電気的特性が向上することを見出した．SIMS等による解析の結果，酸素がp形GaN中の水素と反応し，Mgアクセプタを活性化していることがわかった．

Japanese Journal of Applied Physics, Part 1 (Regular Papers & Short Notes)


Selective etching of GaN over AlxGa1-xN using Reactive Ion Plasma of Cl2/CH4/Ar gas Mixture


Nucleation Control in the Growth of Bulk GaN by Sublimation Method