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在金属有机化学气相外延(MOVPE)生长GaN薄膜的反应-输运过程数值模拟中,反应动力学参数(活化能和指前因子)的选取存在很大的不确定性,从而导致不同的气相反应路径和生长速率.本文对前人采用的反应动力学参数的偏差做了归纳总结,讨论了偏差的来源.在此基础上,本文对垂直转盘式MOVPE反应器生长GaN的反应-输运过程进行数值模拟研究.模拟改变不同的反应动力学参数组合,包括加合物的生成和可逆分解的指前因子、加合物不可逆分解生成氨基物的活化能和指前因子以及三聚物生成的指前因子.通过分析主要含Ga物质的摩尔浓度和对应的生长速率的变化,研究上述反应动力学参数变化对GaN生长反应路径的模拟结果的影响.研究的主要结论如下:(1)不同的指前因子和活化能导致不同的反应路径和生长速率的差异,而热解路径比起加合路径能够更有效地提高生长速率.(2)在不考虑三聚物反应时,预测的生长速率值都与实验值接近.原因在于,输运限制的生长速率取决于含Ga粒子的输运速率,不同的反应路径对含Ga粒子的影响此消彼长,但到达衬底的含Ga粒子的总量变化不大,这也很好地解释了不同文献采用不同的动力学参数模拟都与实验基本吻合的原因.(3)改变三聚物反应的指前因子发现,由于热泳力对大分子的排斥作用,三聚物对生长的贡献很小,生成的三聚物越多,与实验的误差越大.模拟结果澄清了前人在模拟MOVPE生长GaN的反应-输运过程中存在的一些问题,并加深了对GaN生长机理的了解.
In the numerical simulation of reaction-transport processes for the growth of GaN films by MOVPE, the choice of reaction kinetics parameters (activation energy and pre-exponential factors) is highly uncertain, leading to different gas phase reactions Path and growth rate.This paper summarizes the deviation of the reaction kinetic parameters adopted by predecessors, and discusses the source of the deviation.On the basis of this, the reaction of GaN transport in vertical turntable MOVPE reactor Numerical simulations were carried out to simulate different combinations of reaction kinetics parameters, including pre-exponential factors of adduct formation and reversible decomposition, irreversible decomposition of adducts to activation energy and pre-exponential factors of amines, and trimer-generated fingers The influence of the above reaction kinetic parameters on the simulation results of the growth path of GaN was studied by analyzing the changes of the molar concentrations and the corresponding growth rates of the major Ga-containing species.The main conclusions of the study are as follows: (1) Pre-factor and activation energy lead to different reaction path and growth rate differences, and the pyrolysis path than the additive path can be more effective in increasing the growth rate . (2) The predicted growth rate values are close to the experimental values when the trimer reaction is not considered because the transport-limited growth rate depends on the transport rate of the Ga-containing particles and the different reaction paths affect the Ga The effect of the particles is exacerbated, but the total amount of Ga-containing particles reaching the substrate does not change much, which is also a good explanation for the different kinetic parameters in different literatures. It is found that due to the exclusion of macromolecules by thermophoretic force, the contribution of trimer to growth is small, and the more trimer produced, the greater the error with experiment, the result of simulation is clarified The former has some problems in the simulation of reaction-transport of GaN grown by MOVPE, and deepens the understanding of the growth mechanism of GaN.