Photoelectric and electrical properties of a reverse-biased p-Si/n-CdS/n +-CdS heterostructure

Abstract

We have demonstrated a photosensitive p-Si/n-CdS/n+-CdS structure. A reverse bias voltage applied to this structure leads to electron injection from the narrow-band-gap material p-Si to the high-resistivity, wide-band-gap semiconductor n-CdS. Evidence is presented for mutual compensation of opposite drift and diffusion flows of charge carriers in this structure. At current densities in the range I ∼ 10−8 to 10−7 A/cm2, the opposite drift and diffusion flows of nonequilibrium minority charge carriers cause the photosensitivity of the structure to change sign in both the short- and long-wavelength regions of the spectrum. The mutual compensation of the opposite drift and diffusion flows at current densities on the order of ∼106 A/cm2 leads to sublinear behavior of the reverse current-voltage characteristic in a wide range of bias voltages.