Compositional Effects on Solidification of Congruently Melting InSb

In vertical Bridgman and Czochralski growth of stoichiometric electronic materials such as InSb, GaSb, and GaAs, growth from stoichiometric melts is commonly desired to achieve high quality. Off-stoichiometric growth is considered significant in the quest to understand transport phenomena leading to the observed sporadic inclusions. Here we apply radiographic interface visualization and calibrated interface temperature measurements to study growth of InSb from off-stoichiometric melts. The crystals are analyzed for structure and chemical segregation. Results indicate concentration boundary layer formation in the melt ahead of the interface. Evidence is presented for heterogeneous nucleation sites within alpha InSb. Analysis indicates that these nucleation sites develop ahead of the interface in the off-stoichiometric melt phase as the melt temperature at the interface drops below the congruent melting temperature of alpha InSb.