EXPERIMENTAL-DETERMINATION AND NUMERICAL MODELING OF SOLID-LIQUID INTERFACE SHAPES FOR VERTICAL BRIDGMAN GROWN GASB CRYSTALS

A facility, based on a profiled resistive heater, has been designed fo r the growth of antimonide crystals (GaSb, InSb) by the vertical Bridg man method. Solid-liquid interface shapes during the growth of 2-in di ameter crystals are marked by means of variations of the pulling rate and are revealed by chemical etching. The comparison with the calculat ed interface shapes, obtained using a finite element method, gives a s atisfactory agreement. It is shown that the heat transfer and conseque ntly the interface shapes are greatly influenced by the crucible assem bly. For example, small spacings around the crucible or slots in the c rucible holder can change the interface curvature from convex to conca ve. 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 rese rved.