Photoconductive properties of thin-film heterojunction ZnSe-(Zn1-xCdxTe)1-y(In2Te3)y

We have developed a high quantum efficiency and a low dark current photosensor with thin-film heterojunction ZnSe-(Zn1-xCdxTe)1-y(In2Te3)y. This heterojunction has a quantum efficiency of above 0.9 in the wavelength range of 400-750 nm and the dark current is 1.5-5.0 nA/cm²at reverse bias of about 15 V. These excellent characteristics can be obtained by adopting the blocking type heterostructure and optimizing the composition and . The roles of each layer of this heterojunction are analytically discussed. The ZnSe film works as a blocking layer for the holes injected from the transparent electrode, reducing the dark current. The (Zn1-xCdxTe)1-y(In2Te3)yfilm is a photosensitive layer and blocks the electrons injected from this side of electrode because of its p-type conductivity. The several photoconductive properties of the heterojunction are shown to be dominated by the deep trap states lying near the middle of forbidden energy gap. This photosensor can be applied to several devices such as photocells, facsimile sensors, photoconductors for electroxerography, and photoconductive targets of camera tubes.