Homogenization of zinc distribution in vertical Bridgman grown Cd_0.96Zn_0.04Te crystals

Abstract

One of the most pressing issues in the growth of high quality single crystal Cd _0.96 Zn _0.04 Te material, is to achieve homogenization of the high axial variation of Zn concentration, caused by the larger than unity segregation coefficient of Zn in CdTe. This is achieved in our crystals (i) by thermal annealing of the CdZnTe crystal, which redistributes the as grown Zn distribution by solid state diffusion of Zn (this solid state diffusion of Zn occurs at three stages (a) during the growth when the solidified crystal is near to the melting point temperature, (b) during the post growth annealing of the crystal at a high temperature and (c) during the cooldown to room temperature) and (ii) by the reduction of Zn segregation during the growth stage by enhanced convective mixing of the melt, through a proper choice of ampoule and furnace dimensions. By adopting suitable growth parameters and sufficient post growth annealing it has been possible to grow Cd _0.96 Zn _0.04 Te crystals, which have nearly 75% of their fraction within 1% Zn concentration variation.