Direct measurements of free crystal growth in deeply undercooled melts of semiconducting materials

Bulk melts of semiconducting pure Ge and dilute Ge-based systems were processed in a containerless state. Velocities of free crystal growth have been measured directly as a function of undercooling. The analysis within current theories of dendrite growth allows the identification of the growth mode, either edgewise or continuous, depending on undercooling and Sn concentration. The addition of small amounts of Sn to Ge leads to a substantial enhancement of the growth velocity. This behavior is interpreted within crystal-growth theory by a continuous change of the solid-liquid interface from a faceted to a rough interface.