Effect of Surface Electric Fields on Radiative Recombination in CdS

Abstract

Photoluminescence (edge emission) in a variety of CdS single crystals has been studied under the influence of the surface field generated near the Au–CdS interface of an Au–CdS Schottky-barrier diode. Experimentally, above bandgap radiation is incident upon a semitransparent Au film evaporated on an air-cleaved CdS surface. Free electrons and holes are generated within the region of the high barrier field which extends on the order of 0.5 μ into the crystal bulk. Variations of diode bias as small as 2.5 V were found to be sufficient to alter the luminescence efficiency by nearly two orders of magnitude. A model is presented (emphasizing the rapid removal of photoinjected free carriers from the barrier) which qualitatively accounts for the major features of the observed effects.