Preparation for microgravity science investigation of compound semiconductor crystal growthPreparatory work on Bridgman directional solidification (BDS) of PbSnTe crystals prior to microgravity crystal growth experiments on Shuttle flights are reported. Gravitational effects become important in crystal growth when density gradients are present. The situation is critical in BDS of PbSnTe because of the necessity of obtaining homogeneous compositional distributions, which can be disturbed when convective processes occur. Numerical models have been defined which quantify the effects of convection in the crystal growth solution. The models were verified by earth-based crystal-growth tests in a two-zone furnace using equal concentrations of each of the elements. Data are provided to demonstrate the differences in composition among crystals grown at different orientations to the gravitational field vector.
Document ID
19860031056
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Fripp, A. L. (NASA Langley Research Center Hampton, VA, United States)
Debnam, W. J. (NASA Langley Research Center Hampton, VA, United States)
Clark, I. O. (NASA Langley Research Center Hampton, VA, United States)
Crouch, R. K. (NASA Headquarters Washington, DC United States)
Carlson, F. M. (Clarkson University Potsdam, NY, United States)