Abstract

The impact of carrier gas on the GaN layers properties grown by atmospheric pressure metal-organic vapor-phase epitaxy (AP-MOVPE) on (001) and (11n) GaAs substrates were investigated. The Arrhenius plots of growth rate deduced from laser reflectometry measurements give an activation energy of E_a1 = 0.045 eV when the H₂ was used as the carrier gas. In the case of using N₂ as the carrier gas, the results give E_a2 = 0.081 eV as a value of activation energy, which is approximately 2 times greater than E_a1. Scanning electron microscopy results show that when N₂ is used, the resulting material quality is low, but the use of H₂ is successful to prevent the cracking of GaN layers and results in improvement of crystalline properties. From the X-ray diffraction result, we conclude that both (001) and (113) GaAs substrate orientations as well as the use of H₂ as the carrier gas favors the GaN growth with cubic structure, whereas the GaN hexagonal structure is favored for growth on (112) and (111) GaAs substrates orientations with N₂. Cathodoluminescence measurements show that a mechanism of phase transformation occurs when the growth temperature rise from 800 to 900°C.

中文翻译：

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载气对AP-MOVPE在（001）和（11 n）GaAs衬底上生长的GaN层性能的影响：对比研究

摘要

研究了载气对大气压金属有机物气相外延（AP-MOVPE）在（001）和（11 n）GaAs衬底上生长的GaN层性能的影响。当将H ₂用作载气时，由激光反射法测量得出的Arrhenius生长速率图可得出E _a1 = 0.045 eV的活化能。在使用N ₂作为载气的情况下，结果得出E _a2 = 0.081 eV作为活化能的值，大约是E _a1的2倍。扫描电子显微镜结果表明，当N ₂使用H _2时，得到的材料质量低，但是H ₂的使用成功地防止了GaN层的破裂，并且导致了晶体性质的改善。从X射线衍射结果可以得出结论，（001）和（113）GaAs衬底取向以及使用H ₂作为载气都有利于立方结构的GaN生长，而GaN六方结构则有利于N（₂）在（112）和（111）GaAs衬底上生长。阴极发光测量表明，当生长温度从800℃升高到900℃时，会发生相变机制。