垂直布里奇曼法生长CdZnTe晶体时坩埚下降速度的优化研究

Optimization of Crucible Descending Rate during the Crystal Growth of CdZnTe by a Vertical Bridgman Method

在垂直布里奇曼法(VBM)晶体生长的过程中,坩埚下降速度和晶体生长速度之间的关系对生长出来的晶体质量有很大的影响。本文采用有限元法对探测器材料CdZnTe的晶体生长过程进行了热分析,主要研究了不同的坩埚下降速度对生长过程中晶体生长速度及固液界面形状的影响,发现材料的热导率和相变潜热的比值是影响固液界面形状的主要内因。模拟结果表明,当坩埚下降速度Vp≈1mm/h时,其数值与晶体生长速度接近相等,可获得接近水平的固-液界面。实际的晶体生长实验结果与计算机模拟的结论基本一致。因此,通过适当的选择和调节坩埚下降速度是获得高质量晶体的可行技术方案。

During the crystal growth by VBM, the relationships between crucible descending rate and crystal growth rate greatly influence the crystal quality. In this paper, finite element method (FEM) was used to simulate the growth process of CdZnTe crystal and the effects of different crucible descending rates on crystal growth rate and solid-liquid interface configuration were studied as well. Simulations show that when crucible descends at the rate of about 1mm/h, which nearly equals to crystal growth rate, nearly flat solid/liquid interface and little variation of axial temperature gradient near it can be attained, which are well consistent with the results of experiments. Therefore, CdZnTe crystal with low dislocation density can be obtained by employing and adjusting appropriate crucible moving rate during the crystal growth.