Fabrication of transparent p-NiO/ n-ZnO heterojunction devices for ultraviolet photodetectors

Abstract

An optically transparent p– n heterojunction device consisting of p-NiO and n-ZnO thin films was fabricated by r.f. sputtering method. The structural and optical properties of the p-NiO/ n-ZnO heterojunction were characterized by X-ray diffraction (XRD), UV–visible spectroscopy, Hall effect measurement, and J– V photocurrent measurements. The XRD shows that ZnO films are highly crystalline in nature with preferred orientation along the (0 0 0 2) direction. The p-NiO/ n-ZnO heterojunction device has an average transmittance of over 80% in the visible region. The current–voltage curve of the heterojunction demonstrates obvious rectifying diode behavior in a dark environment. The lowest leakage current is 6.64 × 10 −8 A/cm 2 for the p-NiO/ n-ZnO heterojunction device.