Properties of CdS/ZnCdTe heterojunctions

A series of CdS/ZnxCd1−xTe heterojunctions have been prepared by evaporation of CdS onto single-crystal p-type ZnxCd1−xTe substrates with x=0, 0.1, and 0.3. The junction properties have been evaluated as a function of x, the substrate surface preparation, and the substrate temperature during CdS deposition. The junctions with the best quality correspond to those formed on stoichiometric ZnxCd1−xTe surfaces. Even with the optimum surface preparation, an increase in x results in an increase in the reverse saturation current and a decrease in the open-circuit voltage. Current versus voltage measurements as a function of temperature indicate that the junction transport can be described by thermally assisted tunneling. Illumination increases the junction transport current, an effect that persists for a measurable time after cessation of illumination. Both results can be described in terms of the effects of interface states, controlling tunneling/recombination and the width of the depletion layer in the ZnxCd1−xTe.