共查询到19条相似文献,搜索用时 356 毫秒
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在氢化物气相外延(HVPE)生长GaN厚膜中,反应腔壁面总会产生大量的寄生沉积,严重影响薄膜生长速率及质量.本文针对自制的大尺寸垂直式HVPE反应器,通过数值模拟与实验对比,研究了反应腔壁面沉积以及GaN生长速率的分布规律,特别是寄生沉积分布与载气流量的关系.研究发现:在基准条件下,顶壁寄生沉积速率由中心向边缘逐渐降低,与实验结果吻合;侧壁沉积出现8个高寄生沉积区域,对应喷头边缘处排布的GaCl管,说明沉积主要取决于GaCl的浓度输运;模拟得出的石墨托表面生长速率低于实验速率,但趋势一致.保持其他条件不变,增大NH3管载气N2流量,顶壁和侧壁的寄生沉积速率及分布区域均随之增大,石墨托表面生长速率随之减小而均匀性却随之提高;增大GaCl管载气N2流量,顶壁和侧壁的寄生沉积速率及分布区域均随之减小,石墨托表面生长速率随之增大而均匀性却随之降低.研究结果为大尺寸HVPE反应器生长GaN的工艺优化提供了理论依据. 相似文献
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氮化镓(GaN)晶体是制备蓝绿光激光器、射频微波器件以及电力电子等器件的理想衬底材料,在激光显示、5G通讯及智能电网等领域具有广阔的应用前景.目前市场上的氮化镓单晶衬底大部分都是通过氢化物气相外延(Hydride Vapor Phase Epitaxy,HVPE)方法生长制备的,在市场需求的推动下,近年来HVPE生长技术获得了快速的发展.本论文综述了近年来HVPE方法生长GaN单晶衬底的主要进展,主要内容包含HVPE生长GaN材料的基本原理、GaN单晶中的掺杂与光电性能调控、GaN单晶中的缺陷及其演变规律和GaN单晶衬底在器件中的应用.最后对HVPE生长方法的发展趋势进行了展望. 相似文献
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氮化镓(GaN)具有高击穿场强、高饱和电子漂移速率、抗辐射能力强和良好的化学稳定性等优良特性,是制作宽波谱、高功率、高效率光电子、电力电子和微电子的理想衬底材料.除气相法(包括HVPE(氢化物气相外延)、MOCVD(金属有机化合物化学气相沉淀)、MBE(分子束外延))生长GaN单晶外,液相法(包括氨热法和助熔剂法)近几年在制备GaN单晶方面取得了较大的进展.本文介绍了氨热法和助熔剂法的生长原理、装备特点及生长习性;综述了两种液相生长方法的研究历程及研究进展,并对液相法生长GaN单晶的发展趋势及主要挑战进行了展望. 相似文献
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氮化镓(GaN)作为第三代宽禁带半导体核心材料之一,具有高击穿场强、高饱和电子漂移速率、抗辐射能力强和良好的化学稳定性等优良特性,是制作宽波谱、高功率、高效率光电子、电力电子和微电子的理想材料.受制于氮化镓单晶衬底的尺寸、产能及成本的影响,当前的GaN基器件主要基于异质衬底(硅、碳化硅、蓝宝石等)制作而成,GaN单晶衬底的缺乏已成为制约GaN器件发展的瓶颈.近年来,国内外在GaN单晶衬底制备方面取得了较大的进展.本文综述了氮化镓单晶生长的最新进展,包括氢化物气相外延法、氨热法和钠助熔剂法的研究进展,分析了各生长方法面临的挑战与机遇,并对氮化镓单晶材料的发展趋势讲行了展望. 相似文献
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使用金属有机化学气相沉积法生长了AlGN/GaN高电子迁移率晶体管.研究了生长压力和载气组分对AlGaN势垒层及AlGaN高电子迁移率晶体管二维电子气迁移率的影响.原子力显微镜(AFM)光谱和SEM-EDS用于表征外延层的质量.结果表明随着反应室压力从50torr提高到200torr,AlGaN势垒层的表面形貌先变好,随后开始变差.在反应室压力100torr情况下得到最好的表面形貌.同时发现在生长AlGaN势垒层时,同时适当的氢气会提高AlGaN层的质量.在反应室压力100torr、氢气组分59;时得到AlGaNHEMT的最大二维电子气迁移率为1545 cm2/V·s. 相似文献
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以低速旋转、加高喷头、垂直喷淋的MOCVD反应室为对象,运用三维数学输运模型分析与计算.在模拟过程中分析了压强的变化对高喷头反应室流场的影响,着重分析与讨论了操作压强变化与GaN薄膜的沉积一致性及平均生长速率的关系,其次探讨了实验值与模拟值对比结果,从而对薄膜的均匀性及平均生长速率进行一定的预测,最终得到以基准工艺参数为前提的最佳压强设定范围为6650~13300 Pa.模拟跟实验结果表明:减小压强有利于薄膜的均匀性,压强较大时,平均生长速率大,但压强较大时极易引起流场不稳. 相似文献
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E. Richter U. ZeimerS. Hagedorn M. WagnerF. Brunner M. WeyersG. Tränkle 《Journal of Crystal Growth》2010,312(18):2537-2541
The boule-like growth of GaN in a vertical AIXTRON HVPE reactor was studied. Extrinsic factors like properties of the starting substrate and fundamental growth parameters especially the vapor gas composition at the surface have crucial impact on the formation of inverse pyramidal defects. The partial pressure of GaCl strongly affects defect formation, in-plane strain, and crystalline quality. Optimized growth conditions resulted in growth rates of 300–500 μm/h. GaN layers with thicknesses of 2.6 and of 5.8 mm were grown at rates above 300 μm/h. The threading dislocation density reduces with an inverse proportionality to the GaN layer thickness. Thus, it is demonstrated that growth rates above 300 μm/h are promising for GaN boule growth. 相似文献
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Tzu-Tao Yuan Ping-Yu Kuei Li-Zen Hsieh Ta-Ching Li Wen-Jen Lin 《Journal of Crystal Growth》2010,312(15):2239-2242
We studied the effect of gas flow ratio of the H2 carrier gas to the NH3 precursor on the physical and crystal properties of GaN. GaN was grown by vertical reactor metalorganic chemical vapour deposition (MOCVD) on a low-temperature-deposited GaN buffer layer. A (0 0 0 1) sapphire substrate was used. The impact of the gas flow ratio as it was varied from 0.25 to 1 was investigated and discussed. With increase in flow ratio, the concentrations of magnesium and carbon impurities in GaN increased. The flow ratio of 0.5 is the optimum value to minimise the background electron concentration and to maintain crystal quality. The decrease in the background electron concentration is due to the compensation mechanism of acceptor-like magnesium and carbon impurities. 相似文献
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H.Y. Kwon M.J. Shin Y.J. Choi J.Y. Moon H.S. Ahn S.N. Yi S. Kim D.H. Ha S.H. Park 《Journal of Crystal Growth》2009,311(16):4146-4151
We fabricated one-dimensional GaN nanorods on AlN/Si (1 1 1) substrates at various temperatures, and carrier gas flow amount, using the hydride vapor phase epitaxy (HVPE) method. An AlN buffer layer of 50 nm thickness was deposited by RF sputtering for 25 min. Stalagmite-like GaN nanorods formed at a growth temperature of 650 °C. The diameters and lengths of GaN nanorods increase with growth time, whereas the density of nanorods decreases. And we performed the experiments by changing the carrier gas flow amount at a growth temperature of 650 °C and HCl:NH3 flow ratio of 1:40. GaN nanorods, with an average diameter of 50 nm, were obtained at a carrier gas flow amount of 1340 sccm. The shape, structures, and optical characteristics of the nanorods were investigated by field-emission scanning electron microscopy, X-ray diffraction, and photoluminescence. 相似文献
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Si-Young Kim Hyun-Jae Lee Seung-Hwan Park Woong Lee Mi-Na Jung Katsushi Fujii Takenari Goto Takashi Sekiguchi Jiho Chang Gyungsuk Kil Takafumi Yao 《Journal of Crystal Growth》2010,312(14):2150-2153
A new hydride vapor phase epitaxy (HVPE)-based approach for the fabrication of freestanding GaN (FS-GaN) substrates was investigated. For the direct formation of low-temperature GaN (LT-GaN) layers, the growth parameters were optimized: the polarity of ZnO, the growth temperature, and the V/III ratio. The FS-GaN layer was achieved by gas etching in an HVPE reactor. A fingerprint of Zn out-diffusion was detected in the photoluminescence measurements, especially for the thin (80 μm) FS-GaN film; however, a thicker film (400 μm) was effectively reduced by optimization of GaN growth. 相似文献
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E. Aujol A. Trassoudaine L. Siozade A. Pimpinelli R. Cadoret 《Journal of Crystal Growth》2001,230(3-4):372-376
This study presents the influence of the composition of the carrier gas on the growth of GaN by HVPE. Since no hydrogen is introduced in the vapour phase, the deposition is expected to be controlled by Cl desorption in the form of GaCl3, as has been proposed for GaAs. However, our published model predicts much lower growth rates than those observed. We can account for both the observed parasitic deposition and GaN growth rate if we assume that GaCl3 is not at its equilibrium pressure in the deposition zone and where nucleation takes place on the walls as well as on the substrate. This yields a high rate of parasitic nucleation even though the nominal supersaturation is vanishing small. Very little growth takes place on the substrate where the equilibrium pressure of GaCl3 is reached. We describe similar experiments performed with a H2/N2 mixture as the carrier gas. In this case, we expect GaN deposition to be controlled by desorption of Cl as HCl, which is known as the H2 mechanism. It is speculated that the results show the existence of a new growth mechanism. 相似文献
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S. Krukowski P. Kempisty P. Strk G. Nowak R. Czernecki M. Leszczynski T. Suski M. Bockowski I. Grzegory 《Crystal Research and Technology》2007,42(12):1281-1290
Surface properties and the principal processes at the growth of gallium nitride on GaN (0001) face in ammonia‐based are modeled using DFT (density functional theory – SIESTA code) ab initio calculations and 2‐d diffusion analysis. The GaN growth methods are: ammonia‐source MBE, MOVPE, and also HVPE. The adiabatic trajectories, calculated for hydrogen‐rich and hydrogen‐free state of the GaN(0001) surface, include the adsorption of NH3, GaCl and HCl molecules and the desorption of Ga atoms. The adsorption of ammonia and GaCl has no energy barrier. Thus, in contrast to the results concerning Plasma‐Assisted Molecular Beam Epitaxy (PA MBE), proving that the GaN(0001) surface remains in metal‐rich state, these results indicate that, in the ammonia‐rich environment, typical for HVPE and MOVP growth, the GaN(0001) surface remains in the nitrogen‐rich state. In the case of HCl adsorption, the energy barrier depends on the surface coverage, and could reach 2.0 eV. The direct desorption of single Ga atom has the energy barrier, close to 7 eV. This indicates that Ga surface diffusion (growth controlling process) length is very large, leading to strong interaction of the step kinetics and the diffusion on the terraces. This interaction leads to double–step intertwined structures both in the case of dislocation‐mediated spiral growth and in the step flow growth mode. These morphologies, proposed by the geometric arguments, are observed in the atomic force microscopy (AFM) scans of the GaN(0001) surface. Additionally we have compared the interaction energy of two hydrogen atoms obtained in the DFT SIESTA and the high precision Gaussian in coupled cluster singles, double and perturbation triples CCSD(T) approximation. Both approaches yielded virtually identical interaction energy confirming the validity of DFT analysis of ammonia‐rich growth of GaN. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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A.S. Segal A.V. Kondratyev S.Yu. Karpov D. Martin V. Wagner M. Ilegems 《Journal of Crystal Growth》2004,270(3-4):384-395
A simple quasi-thermodynamic model of surface chemistry in GaN hydride vapor phase epitaxy (HVPE) is presented. The model is coupled with the detailed 3D simulations of species transport in a horizontal-tube reactor and validated by the comparison with the data on the GaN growth rate obtained by laser reflectometry. Parametric study of the growth rate as a function of temperature and species flow rates has been performed over a wide range of growth conditions. The important role of species transport in an HVPE reactor is demonstrated. In particular, a strong effect of the natural concentration convection resulting in the formation of recirculation zones and in a non-uniform vapor composition is revealed by modeling. The impact of these effects on the GaN growth rate and V/III ratio on the growth surface is discussed in detail. 相似文献
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J. Skibinski P. Caban T. Wejrzanowski G.J. Oliver K.J. Kurzydlowski 《Crystal Research and Technology》2016,51(12):762-770
The paper presents the results of numerical simulations and experimental measurements of the epitaxial growth of gallium nitride in Metal Organic Vapor Phase Epitaxy within a AIX‐200/4RF‐S reactor. The aim was to develop optimal process conditions for obtaining the most homogeneous crystal layer. Since there are many factors influencing the chemical reactions on the crystal growth area such as: temperature, pressure, gas composition or reactor geometry, it is difficult to design an optimal process. In this study various process pressures and hydrogen volumetric flow rates have been considered. Due to the fact that it is not economically viable to test every combination of possible process conditions experimentally, detailed 3D modeling has been used to get an overview of the influence of process parameters. Numerical simulations increased the understanding of the epitaxial process by calculating the heat and mass transfer distribution during the growth of gallium nitride. Appropriate chemical reactions were included in the numerical model which allowed for the calculation of the growth rate of the substrate. The results obtained have been applied to optimize homogeneity of GaN film thickness and its growth rate. 相似文献
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气体流量及配比对CVD SiC膜层的影响 总被引:1,自引:0,他引:1
本文以甲基三氯硅烷(MTS)为先驱体原料,H2为载气,采用化学气相沉积工艺在反应烧结碳化硅表面制备SiC致密膜层。研究了不同反应气体流量及配比对CVD碳化硅膜层的影响。结果表明:反应气体的流量对膜层的表面形貌影响较大,较大的气流量容易使膜层剥落;减小反应气体流量有利于改善膜层的均匀性。H2/MTS比例影响沉积SiC膜层的相组成。当沉积温度为1200℃,H2/MTS比例为6∶1时,得到的膜层由SiC和C两相组成;当H2/MTS比例为12∶1时,膜层由SiC和Si两相组成;当H2/MTS比例为10∶1时,得到单一相的SiC膜层。在优化的工艺参数下,制备出致密的CVD膜层,经过光学加工后膜层的表面粗糙度为0.72 nm,平面度RMS为0.015λ(λ=0.6328μm)。 相似文献