Sensitivity of Doped Semiconductor Melts to Microgravitation during Crystallization in Space

Abstract

A new approach has been suggested for evaluating the sensitivity of doped crystallization systems to microgravitation. The approach is based on the differential analysis of the Burton-Prim-Slichter equation under the boundary conditions characteristic of the growth processes on board spacecrafts. A new quantity has been introduced into consideration—a sensitivity coefficient to microgravitation, K s , proportional to the change of the dopant concentration C s in a growing crystal under the constant dynamical conditions resulting in the diffusion of the boundary δ -layer in the melt. The K s values are calculated for electrically active "small" dopants in Ge and Si crystals. It is shown that the degree of impurity and electrophysical inhomogeneity in crystals grown under the same microgravitation conditions on board a space vehicle is essentially dependent on the dopant type. The principles of choosing dopants, as well as some technological procedures for reducing non- controllable factors affecting the impurity homogeneity of semiconductor single crystals grown onboard a spacecraft, are developed. © 2000 MAIK "Nauka/Interperiodica".