p-Type Photoconductivity and Infrared Quenching in Electron-Bombarded CdS

Abstract

A platelet‐type crystal of pure cadmium sulfide 46 μ thick was irradiated first with 100‐kev electrons to reduce the number of sulfur interstitials, than for 400 μa‐hr/cm² with 150‐kev electrons to produce an excess of sulfur vacancies. At room temperature, photoconductive peaks were observed at 0.67, 0.9, and 1.4 μ. Point‐contact rectification was used to determine that the 0.67‐μ peak was due to electronic conduction and the 0.9‐ and 1.4‐μ peaks were due to hole conductivity. A ``quenching'' experiment, i.e., simultaneous irradiation with bandgap light and infrared light of variable wavelength, at room temperature shows the 0.67‐μ photopeak and quenching at 0.9 and 1.4 μ. In a separate experiment, the 1.4‐μ quenching band was partially removed from a platelet‐type crystal by bombarding at 100 kev. This bombardment also removed edge emission from this crystal. The temperature dependence of the 1.4‐μ quenching band and of the intensity of edge emission as observed by Reynolds suggests that the centers for edge emission and for the 1.4‐μ quenching bands are actually the same center, namely the sulfur interstitial in different ionization states.