GERMANIUM PARTITIONING IN SILICON DURING RAPID SOLIDIFICATION

Pulsed laser melting experiments were performed on GexSi1-x alloys (x less than or equal to 0.10) with regrowth velocities ranging from 0.25 to 3.9 m/s. Analysis of post-solidification Ge concentration profiles, along with time-resolved melt depth measurements, allowed determination of the liquid-phase diffusivity D-l for Ge in Si and the dependence of the Ge partition coefficient k on interface velocity. v. A D-l of 2.5 x 10(-4) cm(2)/s was measured. The k vs v data were analyzed using various models for partitioning, including both the dilute and nondilute Continuous Growth Models (CGM). Extrapolating to zero velocity using the partitioning models, an equilibrium partition coefficient of approximately 0.45 was obtained. Best fitting of partitioning data to the nondilute CGM yields a diffusive speed of 2.5 m/s. These measurements quantify previous indications of partitioning observed in other studies of pulsed laser processed GexSi1-x alloys. (C) 1995 American Institute of Physics.