Three-dimensional analysis of flow and segregation control by slow rotation for Bridgman crystal growth in microgravity

Although the buoyancy convection in the melt during crystal growth is greatly reduced in microgravity, the residual gravity, or the so-called g-jitter effect, can lead to three-dimensional (313) unsteady flow and severe radial dopant segregation. Using a centrifuge to rotate the system about the growth axis could be an effective way to suppress the 3D flow and improve dopant uniformity. Through fully time-dependent 3D simulation of Bridgman growth of gallium-doped germanium crystals, we investigate the feasibility of using a centrifuge at low rotation rate to improve the dopant uniformity in the grown crystal. In this numerical model, in addition to the heat flow and the moving interface, both radial and axial segregations are also computed simultaneously for a growth period. The effect of slightly eccentric rotation is also considered and they can be an issue in practical implementation. (C) 2002 Elsevier Science B.V. All rights reserved.