Electron trapping effects in cadmium sulphide

Abstract

This work is an attempt to determine the origin and. behaviour of the defect centres in the forbidden gap of cadmium sulphide. The methods of measurement used were thermally stimulated current and infra-red luminescence techniques. After introductory chapters on semiconductor theory and the material, cadmium sulphide, the published results on T.S.C. and infra-red luminescence measurements are surveyed and analysed. Results are then given for a series of samples with varying degrees of sulphur doping. During the work, the need for a more accurate method of T.S.C. curve analysis arose, and the curve fitting technique was developed for this purpose. It was found to have many advantages over existing techniques. The combination of T.S.C. and infra-red techniques led to the identification of the centres involved in the infrared luminescence. Important traps at O.48, 0.62 and O.84 eV below the conduction band are identified, and their photochemical reactions with the luminescent centres described. It is shown that the luminescent centres are identical with the sensitising centres.