Influence of the dewetting phenomenon on the zinc distribution inCdZnTe crystals grown by dewetted Bridgman technique

摘要

The unusual thermophysical properties (high melt viscosity, large latent heat of fusion, fairly large equilibrium segregation coefficient, etc.) cause considerable difficulty in maintaining uniform zinc composition in the CdZnTe grown crystals. However, industrial applications still require larger high structural quality and homogeneous single crystals with a very low dislocation density, no grains nor twins. These improvements are facilitated by dewetting phenomenon in which the crystal is grown detached from the ampoule wall by a liquid free surface at the level of the solid-liquid interface, called liquid meniscus, which creates a gap between the grown crystal and the ampoule wall.In order to evaluate numerically Zn distribution in CdZnTe crystals grown by dewetted Bridgman technique using a pyrolitic boron nitride (pBN)-coated quartz ampoule, a pseudo quasi-steady state model is considered. The coupled incompressible Navier-Stokes in Boussinesq approximation, convection-conduction and conservative convection-diffusion equations are solved by finite element technique through COMSOL Multiphysics software in the framework of a 2D axisymmetric geometry. Due to the existence of the free surface (meniscus), the Marangoni effect is considered and for its implementation the weak form of the boundary application mode is employed. The effect of the dewetting phenomenon on the zinc distribution is discussed and compared with data reported for crystals grown by classical Bridgman technique.