Three-dimensional convection and asymmetric radial segregation, caused by ampoule tilting during the vertical Bridgman growth, are analyzed using a novel, massively parallel, finite element model. The growth of cadmium telluride with a dilute dopant is considered and found to be surprisingly sensitive to the amount of tilt - as little as one degree of misalignment of the ampoule axis from the gravitational vector produces a significant three-dimensional flow and a concomitant skewing of the dopant distribution along the surface of the growing solid. This indicates the need for precise ampoule axis alignment to ensure process reproducibility. Analysis of the dopant distribution along the solid-liquid interface of the tilted system reveals a surface region more uniform in dopant concentration than any corresponding region of the interface of the perfectly aligned system. For systems in which low radial segregation is very important, growth with an intentional axis offset may be beneficial.
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We would like to thank the reviewers for pointing out ways to improve the discussion of our results. This work was supported in part by Johnson Matthey Electronics, Inc., under contract MDA972-91-C-0046, IR Materials Producibility, from the Advanced Research Projects Agency, Microelectronics Technology Office, and by the National Science Foundation under grant number DMR-9058386. Computational resources were provided by the University of Minnesota Supercomputer Institute and the Army High Performance Computing Research Center under the auspices of the Department of the Army, Army Research Laboratory cooperative agreement DAAH04-95-2-0003/contract DAAH04-95-C-0008,
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