Effective photoelectric converters of ultraviolet radiation with graded-gap ZnS-based layers

Abstract

The use of ultrathin (∼10 nm) stable p-Cu1.8S films as a transparent component of the p-Cu1.8S-n-ZnS heterojunction as well as of the graded-gap layers made it possible to obtain effective photoconverters of ultraviolet radiation. The results of examination of the properties of photoactive Cu1.8S-ZnS junctions grown on the CdS or CdSe substrates with intermediate graded-gap layers CdS-ZnxCd1 − xS or CdSe-(ZnS)x(CdSe)1 − x, respectively, are presented. With the correct selection of parameters of the substrates, the graded-gap layers allows one to attain the optimal characteristics of the p—n junction, to realize high electric fields at the Cu1.8S-ZnS contact, and to solve the problem of fabrication of the back ohmic contact to ZnS without additional doping of all components of the heterostructure with a foreign impurity. Varying the thickness of a thin ZnS layer, it is possible to control the extension of the space charge in the graded-gap layer and thereby to control the long-wavelength edge of photoconverter sensitivity.