Numerical Investigation on the Effects of InSb Geometry on the InGaSb Crystal Growth Under Microgravity

In_xGa_1−xSb single crystals have been grown by using a GaSb/InSb/GaSb-sandwich system onboard at the International Space Station (ISS) via vertical gradient freezing method (VGF). In order to investigate the effects of InSb geometry on the InGaSb crystal growth under microgravity and further optimize the future space experiment, two-dimensional axisymmetric numerical simulations were carried out with different thicknesses and diameters of the InSb crystals. Simulation results showed that enough solutes from feed through diffusion is necessary for the crystal growth process and the InSb thickness will affect the axial Ga concentration gradient and therefore affect the crystal growth rates under microgravity. In addition, results also showed that a larger diameter for the InSb crystal will increase the volume crystal growth rates with a flatter shape for the grown crystal interfaces. In summary, simulation suggests a 2 mm or 3 mm thickness and a 12 mm diameter as the geometry of InSb for future space experiments.