Purity and minority carrier lifetime in silicon produced by direct electrolytic reduction of SiO2 in molten CaCl2

Abstract

Si powder was produced by direct electrolytic reduction of SiO2 in molten CaCl2 at 1123 K. From the Si powder, Si ingots were obtained by a floating zone method. The concentrations of most metallic elements and of P in the Si ingots were lower than the acceptable levels for solar grade Si. The minority carrier lifetimes in the Si ingots were measured using a microwave photo conductivity decay method. The obtained values of ca. 1.0 μs were two orders of magnitude shorter than those observed in an Si ingot prepared from 10N purity Si.