Ultra-thin Tunnel Oxides Formed by Field-induced Anodisation for Carrier-selective Contacts

Abstract

Tunnel oxides for carrier-selective contacts must be sufficiently thin that carriers can tunnel through the oxide whilst minimising recombination at the silicon interface if high open circuit voltages are to be achieved. We report the formation of ultra-thin silicon oxide layers by a field-induced anodisation process in which the anodisation current is directed through the wafer in such a way that very uniform oxides can be grown. Spectroscopic analyses of these thin silicon oxide layers demonstrate the ability to adjust their atomic density and valence band offset by varying the anodisation conditions, suggesting that anodisation may provide a viable method to form tuneable silicon oxide layers for carrier selectivity.