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.