The influence of gravity on crystal defect formation in InSb-GaSb alloys

Abstract

InxGa1−xSb melts with x = 0.5, 0.3 and 0.1 were solidified by a gradient freeze technique on earth and in Skylab 3 and Skylab 4. The three ingots processed in Skylab 3 had diameters less than those of their carbon-coated silica ampoules, while those processed in Skylab 4 (with a higher initial heater temperature) completely filed their ampoules. All six of the earth-processed ingots were sufficiently bireflectant that grains and twins were easily observed with incident polarized light. This was true of only space-processed ingot, the others requiring sandblasted surfaces and oblique lighting to observe twins and grains. Twinning was 70% less in the six Skylab ingots than in the corresponding six earth-processed ingots. Microcracks were more numerous in inhomogeneous regions of the ingot. The number of grain boundaries (exclusive of twin boundaries) was about 18% less in the Skylab ingots. The distribution of voids was more uniform in the Skylab ingots.