温度梯度溶液法生长ZnTe晶体时生长界面的优化设计

Optimization of the growth interface during the growth of ZnTe crystal by the temperature gradient solution growth technique

为了优化用温度梯度溶液法(TGSG)生长ZnTe晶体时的生长界面,设计了一种由莫来石圆筒及其内部的圆柱形石墨芯组成的安瓿支撑结构。用有限元的方法数值模拟了这种支撑结构对生长过程中各种传输现象及生长界面形貌的影响。模拟结果显示,晶体生长开始时,溶液内存在上下两个顺时针方向的涡流。随后,靠近生长界面的涡流很快消失,远离生长界面的涡流逐渐缩小,并向溶液顶部移动。生长界面前的对流消失后,ZnTe溶质以扩散形式向生长界面传输。生长界面最开始为凸界面,待生长至晶锭总长度的1/3处时转为平直界面,之后转为凹界面。生长界面深度始终明显小于未采用本支撑结构时的生长界面,也没有出现生长界面的分段现象。这样的生长界面将有利于提高ZnTe晶体的单晶率及结晶质量。

In order to optimize the growth interface during the growth of ZnTe crystal by the temperature gradi- ent solution growth （TGSG） technique, a cylindrical ampoule pedestal is designed, which consists of a mullite sheath and a graphite core. A finite element model is established to simulate the effects of the pedestal on the transport phenomena and the growth interface during the growth. The results show that when the growth be- gins, there are two clockwise vortexes in the solution. The lower one is close to the growth interface and the up- per one occupies the rest of the solution. The lower vortex vanishes very soon, and the upper one keeps shrink- ing and moving upwards. After the lower vortex disappears, the solute （ZnTe） transfers to the growth interface only by diffusion. The growth interface, which is convex first becomes flat when the first third of the ingot has grown, and turns to concave after that. The depth of the growth interface is far less than that in the growth without the pedestal. Distortion of the growth interface in the growth without the pedestal does not occur in the current growth. The optimized growth interface should be helpful to improve the grain size and the crystalline quality.