Growth kinetics studies of silicon LPE from metal solutions

Abstract

Growth kinetics of silicon liquid phase epitaxy (LPE) from metal solutions was studied in pursuit of device-quality layer formation on cast, metallurgical-grade silicon (MG-Si) substrates for solar cells. We report that a mixture of Al and Cu as a solvent for Si enhances solution wetting to the substrate by Al-SiO/sub 2/ reaction, and generates isotropic growth and macroscopically smooth surfaces due to its high solvent power. This solvent system also controls Al incorporation into the layer by proper Al and Cu compositions in the solution. The layer growth rate was calculated with a rough interface/diffusion boundary layer model and was found to be in good agreement with experimental results, indicating only a small boundary layer (/spl sim/0.1 cm) and a silicon diffusivity of /spl sim/2/spl times/10/sup -4/ cm/sup 2//s in the liquid. The thin layer (/spl sim/30 /spl mu/m) grown on the MG-Si substrate has a minority-carrier diffusion length greater than the layer thickness.