Hole Conduction and Photovoltaic Effects in CdS

Abstract

Semiconducting crystals of CdS have been prepared in which the conduction current is carried preponderantly by positive holes. This is indicated by the positive sign of the Hall voltage and the thermoelectric power. The preparation of these crystals, which were heavily doped with 1–2% Cu, is described. Measurements of electrical conductivity, Hall coefficient and thermoelectric power over the temperature range 95-380°k are reported. The results are difficult to interpret, but suggest that conduction occurs via impurity levels due to copper. Similar measurements on some typical n-type semiconducting CdS crystals are reported for comparison purposes Some attempts have been made to prepare p-;n junctions in CdS. Appreciable photovoltaic effects have been found, and the spectral response and rectification characteristics can be explained in terms of a p-n junction model.