Passivation of cut edges of crystalline silicon by heat treatment in liquid water

Abstract

We report on the effective passivation of cut edges of n-type (100) crystalline silicon by forming thin oxide layers achieved by heat treatment in liquid water at 90 °C for 2 h followed by heating in an air atmosphere at 300 °C for 1 h. The mechanical cut with the (110) oriented cleaved edge markedly decreased the photo-induced effective minority carrier lifetime τ eff to 6.9 × 10−4 s, which was 0.22 times the initial value of 3.2 × 10−3 s, and which was maintained by the region 0.5 cm away from the edge. The present passivation treatment resulted in the reduction of τ eff to 0.43, with τ eff values of 4.0 × 10−4 s at the edge and 9.4 × 10−4 s at 0.2 cm from the edge. The analysis with a simple model of carrier diffusion in the lateral direction resulted in the recombination velocity at the cut edge, which was initially higher than 2000 cm s−1, being decreased to 50 cm s−1 by the present treatment, while the recombination velocity at the sample surface was increased from 8 (initial) to 46 cm s−1, probably due to the field-induced depletion effect.