In situ visualization of constitutional supercooling within a Bridgman-Stockbarger system

Constitutional supercooling is studied within the semiconductor material indium antimonide (InSb) during vertical crystal growth from the melt. The starting mixture is stoichiometric In50Sb50. Translation rates are as low as 2 mu m/s. Solid-liquid interface morphology and axial interface positions are monitored in real-time with radioscopic X-ray visualization. The solid-liquid interface temperature is assessed from calibrated thermocouple measurements at the ampoule wall. Results indicate substantial constitutional supercooling of the melt. Elemental segregation is assessed from the visualization of the interface location in a measured temperature profile and from the phase diagram. Temperature data suggest that the interface is in contact with a melt composition close to In62Sb38 (based on the 525.7 degrees C melting temperature of alpha-InSb in a specified phase diagram). That composition reflects significant gravitational segregation in the melt.