The transport phenomena associated with melt-growth of semi-conductor crystals on Earth and in space were investigated for non-dilute pseudo-binary systems with large liquidus-solidus separation. In these systems, heat and mass transfer are coupled through the dependence of the melting point on composition and the presence of thermosolutal convection. Experimental growth studies of PbSnTe in a vertical Bridgman configuration involving melts with initial aspect ratios of 15 and 6.8 exhibit axial and radial Sn segregation indicative of intensive convective mixing in the melt. The present findings point to the need for more precise thermal field control in crystal growth and suggest growth in a microgravity environment if diffusion controlled conditions are to be achieved. An analysis of heat and mass transfer for an idealized Bridgman growth system has been made and gives predictions for the dynamics that can be expected in such a space experiment.
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Acknowledgement--Financial support of this research by the National Aeronautics and Space Administration (Reference No. NSG-7645) is gratefully acknowledged.