CdSxSe1− x photosensitive films: Preparation, properties and use for photodetectors in optoelectronics

Abstract

The physical properties and the preparation conditions of CdS x Se 1− x (0 ⩽ x ⩽ 1) photosensitive films for use in the fabrication of photoresistors are presented. The films were prepared by thermal evaporation and condensation in a quasi-isolated volume in a vacuum, by cathodic triode sputtering and by chemical deposition from aqueous solution. The relations between the film preparation conditions and their structural, electrophysical and photoelectrical properties were studied. Some of the photoelectrical properties can be explained using the classical theory of photoconductivity of “homogeneous” photoconductors on the basis of a scheme of electronic transitions which includes energy levels of recombination and trapping. These energy levels and their values are determined. The peculiarities of the photoconductivity of the “heterogeneous” films (long relaxation times, residual photoconductivity etc.) are explained by the presence of collective macroscopic potential barriers. Both stripe and sandwich structures were obtained. The sandwich structures were investigated using the approximate theory of injection and contact phenomena in order to determine the microparameters of the photodetector and its contact system. Discrete and multi-element photoresistors, position-sensitive and functional photoresistors and electroluminescent image transformers can be manufactured on the basis of the investigated films and their structures.