摘要
在MOCVD反应器中,针对GaN生长中的TMGa分子,推导出热泳力、热泳速度以及扩散速度的计算公式。在低温区,热泳速度大于扩散速度;在高温区则相反。影响热泳力的主要因素为温度梯度和分子直径。水平式反应器内,粒子同时受到热泳速度和扩散速度的影响。在只考虑组分输运以及包括化学反应等两种情况下,通过改变反应器上壁面温度,模拟得到水平式反应器中热泳力对沉积速率以及反应物粒子浓度分布的影响。并与文献中的实验数据对比,验证了模拟结果的正确性。结果显示,由于热泳力的影响,在相同操作条件下高温区H2等小直径粒子的质量分数增大、TMGa和NH3等大分子粒子的质量分数减小。从提高生长速率的角度,需减小上下壁面温度梯度;从沉积均匀性的角度,应使到达下游的反应粒子数增多,故需增大上下壁面温度梯度。
In this study,the expressions for thermophoretic force,thermophoretic velocity and diffusion velocity for TMGa and NH3 molecules in GaN MOCVD growth were derived.In the colder region,the thermophoretic velocity is faster than the diffusion velocity;in the hotter region,it is the opposite.The thermophoretic force is in proportion to the temperature gradient and particle diameter.In the horizontal MOCVD reactor,the particle motion towards the growth surface is balanced by thermophoretic velocity and diffusion velocity.Considering the case of gas transport only and the case including chemical reactions,and by varying the ceiling temperature,the influence of thermophoretic force on the deposition rate and the concentration distribution are numerically simulated.By comparing the simulation results with the experimental values from literature,good correspondence is obtained.The results show that due to the influence of thermophoretic force,near the hot region,the molar fraction of small molecules such as H2 increases,and the molar fractions of large molecules such as TMG and NH3 decrease.To increase the growth rate,more TMGa molecules are required to arrive the substrate.Consequently,the temperature gradient needs to be decreased so that to decrease the thermophoretic force.On the other hand,to increase the deposition uniformity,more TMGa molecules need to reach the downstream of the reactor,thus the temperature gradient need to be increased so that to repel the TMGa molecules strongly by the thermophoretic force.
出处
《人工晶体学报》
EI
CAS
CSCD
北大核心
2011年第4期1033-1038,共6页
Journal of Synthetic Crystals
基金
国家自然科学基金(No.60376006)
江苏省研究生创新计划项目(CX10B_260Z)
作者简介
于海群（1981-），男，山东省人，博士研究生。E—mail：hiqun@hotmail．com
通讯作者：左然，教授，博导。E-mail：hiqun@hotmail．com
