Effect of solid phase heat transfer and wall deposition on crystal growth in physical vapor transport ampoules

Abstract

A numerical investigation of binary component, convective/diffusive physical vapor transport in cylindrical ampoules is presented. We specifically examine the effects of (1) conduction heat transfer within the crystal, and (2) deposition of the vapor onto the ampoule side walls, on the growth rates and growth uniformity of the crystal. A two-dimensional numerical model of heat and mass transfer within the crystal and vapor regions of the ampoule is developed. Calculations are performed for H 2I 2 transport systems in unit and zero gravity conditions. Results indicate that the latent heat release from the depositing vapor can significantly affect the interface temperature distribution of finite-thickness crystals. Depending on the thermal boundary conditions at the crystal side walls, heat transfer within the crystal can either increase or decrease the uniformity of mass flux at the interface. The predicted transport conditions under which heat transfer has a controlling role on crystal growth are consistent with a simplified, one-dimensional analysis of combined heat and mass transfer in PVT ampoules. Calculation results also reveal that deposition of the vapor onto the side walls of the ampoule can lead to highly nonuniform distributions of mass flux at the crystal interface. Furthermore, side wall deposition can result in buoyant recirculation even when the ampoule is oriented in a convectively stable configuration. This phenomenon can result in interface flux distributions that are considerably different than those obtained under zero gravity environments for the same model conditions.