Subband gap photoresponse of nanocrystalline silicon in a metal-oxide-semiconductor device

In this paper we report on the photoconduction and photovoltaic properties of nanocrystalline silicon. Silicon nanocrystals (Si-ncs) have been prepared by using plasma-enhanced chemical vapor deposition on a p-type silicon substrate. The Si-ncs have been formed into the dielectric of a metal-oxide-semiconductor device. I-V characteristics of the devices have been studied under dark and illumination. Illumination was performed with light in the wavelength range of 350-1630 nm. A photovoltaic effect has been observed in the illuminated I-V characteristics in the range of 350-1100 nm. For longer wavelengths no measurable photovoltaic effect has been observed, but considerable photocurrent has been measured for 1300-1630 nm light under reverse bias condition. This photoresponse is attributed to absorption through subband gap states at the Si-nc and silicon oxynitride matrix interface. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.2999561]