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 90oC for 2 h followed by heating in air atmosphere at 300oC for 1 h. The mechanical cut with the (110) oriented cleaved edge markedly decreased the photo-induced effective minority carrier lifetime τeff to 6.9×10-4 s, which was 0.22 times the initial value of 3.2×10-3 s which the region 0.5 cm apart from the edge maintained. The present passivation treatment improved reduction of τeff to 0.43, for which τeff were 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 that the recombination velocity at the cut edge, which was initially higher than 2000 cm/s, was decreased to 50 cm/s by the present treatment, while the recombination velocity at the sample surface was increased from 8 (initial) to 46 cm/s probably because of field-induced-depletion effect.