CdTe crystal growth process by the Bridgman method: numerical simulation

Abstract

Numerical simulation of the CdTe crystal growth process by the Bridgman method is made by using the commercial computational code FLUENT for the mathematical solution of the governing equations. To reduce computational effort, we have made use of a two level strategy. In the first level we have considered the whole system formed by the ampoule with the liquid–solid charge, the furnace, and the air between them. The heat transfer is assumed to occur by conduction, convection and radiation between the furnace and the ampoule, and only by conduction through the ampoule wall and the solid and liquid CdTe. In the second level we focus on the ampoule and its content, using the values of the temperature field that were calculated in the first level as thermal boundary conditions at the ampoule wall. Heat transfer through CdTe is described at this level by conduction and convection. The phase change has been modeled using an enthalpy-porosity formulation. The calculation of the growth rate at the beginning of the growth shows that this growth rate can be very different from the ampoule translation rate, depending on geometrical and thermal conditions. We analyse the growth rate, axial temperature gradient, concavity of liquid/solid interface and convective flow field in the melt corresponding to the use of ampoules with two different tip geometries (conical and flat) and three graphite cover thicknesses.