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.