Growth and Characterization of Doped Ge Crystals under µg and 1 G to Investigate the Influence of Different Convection Types

Abstract

Three Bridgman growth experiments were performed during the FOTON M4 mission in 2014. The aim of these experiments was to determine the influence of different convective states within the melt volume on the properties of the growing crystal. Transitions between different melt flow regimes were enforced during the ongoing growth by the application of rotating magnetic fields of different strengths and vibrations of different amplitude. A significant influence of the melt flow conditions on the Ga incorporation in the Ge crystal was observed for the µg crystals. The 1 G reference crystals, grown as well in the POLIZON 2 furnace (flight model) with the same parameters, showed always the expected dopant distribution as predicted by Scheil for complete mixing conditions. The buoyancy convection dominates the melt convection induced by the different RMFs or vibrations. The crystals were investigated by Differential Interference Contrast microscopy after structural etching, synchrotron topography to determine the structural quality, and spatially resolved resistivity measurements to determine the axial Ga segregation.