Influence of convection on zinc selenide single crystal growth by chemical vapour transport

Substrate-quality ZnSe single crystals have been grown by process optimized chemical vapour transport. In this connection, a computational procedure is used as an engineering tool to design a series of experiments targeting at the same total transport rate while every experiment exhibits another share of the convective transport modus. By evaluating experiments with a definite share of convective mass transport between 10 and 80%, a tendency to progressive deterioration of morphological stability and crystal perfection has been stated. In order to reduce kinetic limitations at the growing interface, constant values of total growth rate (3.5 X 10(-8) mol cm(-2) s(-1)) and growth temperature (750 degrees C) were adjusted for all these experiments. For this, special data pairs of iodine charge and temperature difference have been determined via mass transport calculations taking into consideration diffusion, Stefan flow and convection. Diffusion-dominated transport conditions reduce the nucleation density and favour the growth of highly perfect ZnSe single crystals.