Experimental determination and numerical modelling of solid-liquid interface shapes for vertical Bridgman grown GaSb crystals

A facility, based on a profiled resistive heater, has been designed for the growth of antimonide crystals (GaSb, InSb) by the vertical Bridgman method. Solid-liquid interface shapes during the growth of 2-in diameter crystals are marked by means of variations of the pulling rate and are revealed by chemical etching. The comparison with the calculated interface shapes, obtained using a finite element method, gives a satisfactory agreement. It is shown that the heat transfer and consequently the interface shapes are greatly influenced by the crucible assembly. For example, small spacings around the crucible or slots in the crucible holder can change the interface curvature from convex to concave. From numerical simulations it is also shown that convection in the melt flattens the interface but that an increase of the pulling rate has the reverse effect. (C) 1998 Elsevier Science B.V. All rights reserved.