Numerical simulations of SiGe crystal growth by the traveling liquidus-zone method in a microgravity environment

Recently, a Si1−xGex (approximately x=0.5) crystal has been grown by the traveling liquidus-zone (TLZ) method under microgravity condition in the International Space Station (ISS). In this work, a mathematical model of the TLZ crystal growth has been developed to investigate details of the transport and solidification phenomena occurred during the TLZ growth of SiGe crystals performed in the ISS. Using this model, the experimental Ge concentration distributions in the grown SiGe crystal is explained, and the emissivity variation of the metal cartridge surface due to oxidation during the crystal growth is revealed to strongly affect the Ge concentration distribution in the grown crystal. In addition, a strategy for growing SiGe crystals, which are more homogeneous than those obtained in the current experiment, is proposed on the basis of the numerical results.