Photovoltage at the metal-CdS Schottky contact

Photovoltages at a metal-CdS Schottky contact occur at photon energies that are smaller than the CdS band gap. They may be due either to photoemission of electrons from the metal into the CdS or to hole generation in the CdS. The first mechanism is shown to occur in conducting CdS. From its observation values for the attenuation length of the photoexcited electrons in Au are derived as a function of photon energy. The second mechanism is shown to occur in insulating CdS. At intermediate conductivities of the CdS photoemission is found for small photon energies, while minority carrier generation in the CdS is responsible for the generation of a photo-e.m.f. at somewhat higher photon energies. (author)