PHOTOLUMINESCENCE EFFICIENCY AND PHOTOCONDUCTIVITY IN CADMIUM SULFIDE

Abstract

The photoluminescence efficiency and photoconductivity response of high-purity cadmium sulfide crystals were measured and interpreted in terms of a simple model involving only the donor and acceptor levels previously established, an effective surface recombination velocity, and a bulk nonradiative recombination rate. The measurements at 64 and 78 °K included the effects on the photoluminescence efficiency of varying the excitation intensity and the wavelength of the excitation light, applying electric fields, removing chemically adsorbed oxygen ions from the surface, and of different acceptor concentrations. It was established that the surface does play an important role in reducing the photoluminescence efficiency and photoconductive response, and that the photogenerated carriers do not diffuse significantly into the interior of the crystal.