Dissolution and growth process of indium gallium antimonide crystal under different gravity levels

To explore the mechanisms of heat and mass transfer, as well as the crystal dissolution and growth/solidification process of indium gallium antimonide (InGaSb) crystals using the vertical gradient freezing method under various gravity conditions, two-dimensional axisymmetric numerical simulations were conducted. Numerical simulations were performed under conditions ranging from zero gravity to terrestrial gravity (1.0 G), including microgravity levels (1 x 10(-6) G, 1 x 10(-4) G, 1 x 10(-3) G, and 1 x 10(-2) G), small gravity (0.1 G), and lunar gravity (0.17 G). Comparisons were made between the simulation and experiments for InGaSb crystal growth under microgravity (1 x 10(-4) G) and terrestrial gravity (1.0 G) and successfully validated the numerical model. Simulation showed that the heat transfer during the dissolution and growth of InGaSb crystal growth was insensible to gravity level variations. Results indicated that the dissolution of feed crystals was consistently dominated by diffusion. However, under microgravity conditions up to 1 x 10(-4) G, both solute transport and seed crystal dissolution processes were diffusion-dominant, while they shifted to convection-dominant at gravity levels above 1 x 10(-2) G, which also caused wavy interface shapes for seed crystals. Furthermore, natural convection caused by small and terrestrial gravity levels inhibited solute accumulation at the seed center while enhancing it at seed periphery, leading to a more concave interface shape, and consequently reduced radial homogeneity and crystal quality of the grown InGaSb crystals. Last, a non-dimensional number was introduced to describe the effect of natural convection under different gravity levels on solute transportation mechanisms during the dissolution and growth/solidification process of InGaSb crystal growth.