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Germanium Partitioning and Interface Stability During Rapid Solidification of Gesi Alloys

Published online by Cambridge University Press:  21 February 2011

D. P. Brunco
Affiliation:
Department of Materials Science and Engineering, Cornell University, Ithaca, NY 14853
Michael O. Thompson
Affiliation:
Department of Materials Science and Engineering, Cornell University, Ithaca, NY 14853
D. E. Hoglundt
Affiliation:
Division of Applied Sciences, Harvard University, Cambridge, MA 02138
M. J. Aziz
Affiliation:
Division of Applied Sciences, Harvard University, Cambridge, MA 02138
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Abstract

The stability of laser processed GeSi heteroepitaxial alloys on Si to partitioning driven interface instabilities is examined. Existing stability models are extended to include nonequi-librium solidification effects for nondilute alloys and are examined under typical conditions of laser induced solidification. Ge diffusion and partitioning were measured for quantitative input to the models. The Ge liquid-phase diffusivity was determined to be 2.5 x 10-4 cm2/s. The measured velocity-dependent partition coefficients k(v) were fit to the Continuous Growth Model using an equilibrium k of 0.45 and a diffusive speed of 2.7 m/s. Stability calculations based on these values and our extended stability model are presented. Although instabilities at compositions comparable to those experimentally observed to give defective films are predicted, the growth rates of these instabilities appear too slow to destabilize an interface on laser processing time scales. These results suggest that strain or other effects play an important role in the observed defective microstructures.

Type
Research Article
Copyright
Copyright © Materials Research Society 1995

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