A numerical study of the buoyancy convection occurring during the formation of InGaSb solution in a GaSb/InSb/GaSb sandwich system

摘要

The formation process of an InGaSb solution in a GaSb/InSb/ GaSb sandwich system was numerically studied by considering the effects of various parameters such as temperature gradient, heating rate, crystal width, thickness of an ampoule wall, and gravity levels. The selected reference temperature at fixed point was increased up to 650℃ (heating process) and then kept constant (holding process). Numerical results showed that under the 1G condition, the solutal buoyancy convection is dominant during the heating process, but its strength gradually decreases during the holding process. The initially symmetric crystal-melt interface becomes asymmetric in shape with the increasing temperature, and then the interface at the end of the heating process broadens towards the bottom of the solution. The deformation of the interface decreases with the increasing temperature gradient. Similar effects were observed with the increase in the thickness of the ampoule wall. This implies that the quartz ampoule plays the role of thermal insulator, As expected, the model shows that a reduced gravity level is very effective in suppressing the buoyancy convection in the solution. In order to achieve a diffusion dominant mass transfer in the solution, the gravity level must to be less than 10~(-4)G.