Modeling the vertical Bridgman growth of cadmium zinc telluride II. Transient analysis of zinc segregation

A transient analysis of the vertical Bridgman growth of large-diameter, cadmium zinc telluride is conducted using a finite element model which accounts for the details of heat transfer, melt convection, solid/liquid interface shape, and zinc segregation. Significant axial and radial segregation is produced by convective mixing in the melt; the system is far from the diffusion-controlled limit. Previous experimental reports of “anomalous” axial segregation are explained by solid-state diffusion mechanisms. Lowering the growth rate is predicted to slightly increase axial segregation but markedly reduce radial segregation. The geometry of the ampoule cone region is shown to significantly affect the initial growth transient.