PHOTOEMISSION FROM Au AND Cu INTO CdS

Many metal-semiconductor surface barrier rectifiers photosensitivity for photon energies (hv) less than the semiconductor energy gap (Eg). in the literature include metals evaporated electrodeposited on elemental and III-V semiconductor surfaces. In these studies source of the low-energy photocurrent, when < Eg, was shown to be the photoemission of over the Schottky barrier between the metal and the semiconductor. An extensive investigation been reported for a series of metals, Cu and Au, electroplated on n-type CdS the conclusion that here also photoemission the metal is responsible for most of the low-energy photovoltage. However, recent studies have this conclusion for the CdS case. One proposed that the origin of the low-energy response is electron photoexcitation Cu impurities located in the CdS and within a length of the space charge region. Hole probably in the 3d Cu levels was postulated these samples, which had ≈ 30-ppm Cu. A second study interpreted the results as a p·n junction photovoltaic effect.