Thermomigration of molten Ga in Si and GaAs

Abstract

Molten zones of Ga have been migrated through Si and GaAs in thermal gradients between 6 and 92°C/cm and over a temperature range between 300 and 1000°C. The observed migration rate is larger in Si than GaAs. In both cases the droplets are faceted on (111) planes. An expression for the migration rate V is derived in terms of the solid's heat of fusion and its solubility in the liquid. For large liquid zones, the calculated rate agrees with experiments for Ga-Si, Al-Si, and Au-Si systems. In contrast, the observed rate for the Ga-GaAs system is lower than calculated because of interface kinetics. In all systems, small liquid zones migrate slower than large liquid zones. Migration rates are also calculated for the Ag-Si, Sn-Si, Sb-Si, and In-Si systems. The general criteria for applying thermomigration in various metal-semiconductor systems are discussed.