NUMERICAL INVESTIGATION ON THE BATCH CHARACTERISTICS OF LIQUID ENCAPSULATED VERTICAL BRIDGMAN CRYSTAL-GROWTH

Since the liquid encapsulated vertical Bridgman (LEVB) crystal growth is a batch process, it is time dependent in nature. A numerical simula tion is conducted to study the unsteady features of the process, inclu ding the dynamic evolution of heat flow, growth rate, and interface mo rphology during crystal growth. The numerical model, which is governed by time-dependent equations for momentum and energy transport, and th e conditions for evolution of melt/crystal and melt/encapsulant interf aces, is approximated by a body-fitted coordinate finite-volume method . The resulting differential/algebraic equations are then solved by th e ILU (0) preconditioned DASPK code. Sample calculations are mainly co nducted for GaAs. Dynamic effects of some process parameters, such as the growth speed, the ambient temperature profile, and ampoule design, are illustrated through calculated results. Due to the heat of fusion release and time-dependent end effects, in some cases a near steady-s tate operation is not possible. The control of growth front by modifyi ng the ambient temperature profile is also demonstrated. Calculations are also performed for a 4.8 cm diameter InP crystal. The calculated m elt/seed interface shape is compared with the measured one from Matsum oto et al. [J. Crystal Growth 132 (1993) 348] and they are in good agr eement.