移动加热器法生长碲锌镉晶体的组分输运与界面形貌研究

Study on Component Transport and Interface Morphology of CdZnTe Crystals Grown by Traveling Heater Method

移动加热器法(THM)生长碲锌镉晶体时,界面稳定性对晶体生长的质量有很大影响。本文基于多物理场有限元仿真软件Comsol建立了THM生长碲锌镉晶体的数值模拟模型,讨论了Te边界层与组分过冷区之间的关系,对不同生长阶段的物理场、Te边界层与组分过冷区进行仿真研究,最后讨论了微重力对物理场分布的影响,并对比了微重力与正常重力下的生长界面形貌。模拟结果表明,Te边界层与组分过冷区的分布趋势是一致的,在不同生长阶段,流场中次生涡旋的位置会发生移动,从而导致生长界面的形貌随着生长的进行发生变化,同时微重力条件下形成的生长界面形貌最有利于单晶生长。因此,在晶体生长的中前期,对次生涡旋位置的控制和对组分过冷的削弱,是THM生长高质量晶体的有效方案。

CdZnTe is one of the most concerned materials for nuclear radiation detection in room temperature semiconductor and traveling heater method(THM)is one of the most promising methods for single crystal CdZnTe growth.The interface stability has a great influence on the quality of CdZnTe crystals grown by THM.In this paper,based on the multi-physical field finite element simulation software Comsol,the numerical simulation model of CdZnTe crystal grown by THM was established.The concept of Te boundary layer was explained,and the relationship between Te boundary layer and constitutional supercooling zone was proposed.The physical field at different growth stages was simulated.The variations of constitutional supercooling zone and Te boundary layer at different stages of growth were analyzed.Finally,the effect of microgravity on physical field of THM was discussed.In order to study the stability of the growth interface,the morphology of growth interface under microgravity and normal gravity was compared.Simulation results show that the distribution of Te boundary layer is consistent with the constitutional supercooling zone.The simulation shows that the secondary vortex which is caused by the inverse temperature gradient at the growth interface front appears.The position of secondary vortex in the flow field of THM changes at different growth stages which leads to the change of growth interface as the growth proceeds.A slight convex or flat growth interface forms when the secondary vortex appears near the crucible wall.Considering the condition of microgravity,a convex growth interface will be formed which is beneficial to the growth of CdZnTe single crystal.Therefore,the control of secondary vortex and decrease of supercooling during the THM growth is an effective scheme for the growth of high-quality CdZnTe crystals under mormal gravity condition.