Study of Photovoltage Decays in Nanostructured Ge/Si

Abstract

Motivated by the importance of the oxidized silicon layers, we have studied the surface photovoltage (SPV) transients in nanoislands of GexSi1x on silicon and oxidized Si surfaces. It is shown that the SPV decays can be approximated by the stretched-exponential form, with the β values ranging from 0.3 to 0.6 for the islands grown on oxide-covered Si substrates and from 0.5 to 1 for the ones placed on bare Si. On this basis, a simple qualitative model is proposed that takes into account a donor-and acceptor-like interface states at the GeSi/SiO2 and Si/SiO2 interface, which act as recombination centers with densities dependent on the GeSi coverage. These results can be used to improve the functionality of photoelectric devices based on Ge/Si.