Numerical investigation of growth interface shape and compositional distributions in SiGe crystals grown by the TLZ method in the International Space Station

•SiGe crystal growth by the traveling liquidus-zone method was carried out in ISS.•The transport phenomena and solidification were investigated by numerical simulation.•Numerical concentration distributions were coincident with the experimental results.•Axial Ge distribution became U-shaped due to the change in cartridge emissivity.•Radial Ge distributions remained relatively uniform throughout the entire crystal. The second and third microgravity experiments on SiGe crystal growth by the traveling liquidus-zone (TLZ) method were carried out aboard the Japanese Experiment Module (JEM) “Kibo” in the International Space Station (ISS) in July 2013 and February 2014. In this study, we numerically investigated the details of transport phenomena and solidification in these two experiments. We found that the deformation of the melt/SiGe crystal interface shape increased with time, and that the growth rate near the crystal edge was much larger than that near the central axis. Comparing the numerical and experimental results of the concentration distribution of Ge, the numerical concentration distributions are reasonably coincident with the experimental ones in both the axial and radial directions. In addition, both numerical and experimental results show that the radial distributions of the Ge concentration remain relatively uniform throughout the entire crystal, although the mean values depend on the growth length.