Optical and Electrical Properties of Nitrogen Doped a-Si: H Films for Solid-State Image Pickup Devices

Abstract

Hydrogenated amorphous silicon (a-Si: H) films deposited by RF sputtering and doped with nitrogen have been found to have high dark resistivity (1013 Ω·cm) and high photoconductivity at a low field. The Fermi level is shifted by 0.2 eV toward the conduction band, compared with undoped film. The spectral response of this film covers the visible region well and a peak quantum efficiency of 1.0 has been obtained at a wavelength of 500 nm. The γ-value of the film is nearly equal to unity for visible radiation. Rise and fall time constants are shorter than 500 µs for a pulsed radiation of 550 nm emitted from an LED. We have found that nitrogen doped n-type a-Si: H films are quite suitable as a photoconductive material for a solid state color imager.