Using the temperature-dependent photovoltage to investigate porous silicon/silicon structures

Structures based on porous silicon por-Si/p-Si, both freshly prepared by chemical etching and aged, exhibit a temperature-dependent photovoltage at high levels of electron-hole pair generation by pulse trains of red and white light. These structures are investigated by measuring this photovoltage, which is shown to consist of two components: a photovoltage generated in p-Si, and an oppositely directed photovoltage that appears in por-Si, characterized by trapping of nonequilibrium holes at the surface of por-Si nanocrystals during the period of illumination by the first pulse of white light. For aged structures capture of electrons in the oxide of the por-Si is also observed. The concentration of interface electronic states and electron traps at the interface of p-Si with por-Si is determined by measuring the photovoltage induced by pulses of red light.