A numerical investigation of the thermal distribution effects in a heat-exchanger-method crystal growth system

Numerical computations have been performed to investigate the effects of the thermal distribution in a heat-exchanger-method crystal growth system on the convexity of the melt-crystal interface and the rate of crystal size increase. Heat transport from the furnace to the crucible is modelled by a convection boundary condition. Two types of environmental temperature distribution outside the crucible are considered: a uniform temperature and an upward temperature gradient. A higher environmental temperature generates higher maximum convexity. During the environmental temperature reduction process, the crystal quickly enlarges in size as the environmental temperature approaches the melting point of the growing crystal. Therefore, decreases in the environmental temperature must be slow to obtain a constant rate of crystal size increase. An upward temperature gradient decreases the convexity of the melt-crystal interface and the hot spot area. The rate of crystal size increase for an upward temperature gradient is less abrupt than it is without the upward temperature gradient. An upward temperature gradient case is more adapted to the maintenance of a constant increase in the crystal size during a decrease in the furnace temperature to near the melting point of the growing crystal.