Infrared Photoconductivity in Heavily Nitrogen Doped a-Si:H

Abstract

AbstractThe generation of high frequency steady-state photoconductivity in nitrogen doped hydrogenated amorphous silicon (a-Si:H-N) films has been demonstrated at infrared (IR) frequencies of 650 to 2000 cm-1 or 15 to 5 μm in wavelength. This allows IR photoconductivity to be observed using a simple thermal source. In order to produce high frequency photoconductivity effects the plasma frequency must be increased to the desired device operation frequency or higher as described by the Drude model. IR ellipsometry was used to measure the steady-state permittivity of the a-Si:H-N films as a function of pump illumination intensity. The largest permittivity change was found to be Δεr = 2 resulting from a photo-carrier concentration on the order of 1022 cm-3. IR photoconductivity is shown to be limited by the effective electron mobility at IR frequencies.