Photosensitivity of ZnO/Cu2O thin film heterojunction

ZnO/Cu2O thin film n–i–p heterojunctions were fabricated by magnetron sputtering. The microstructure and optical properties of n-ZnO and i-ZnO films deposited on glass substrates were characterized by X-ray diffraction (XRD) and spectrophotometer, respectively. The current–voltage (I–V) characteristics of two ZnO/Cu2O n–i–p heterojunctions were investigated, which n-ZnO layer thicknesses were 60 nm and 180 nm. Typical diode rectification behavior was observed in both heterojunctions. The heterojunctions exhibit photosensitivity under the irradiation with a halogen lamp. The dark current and photocurrent are higher in the heterojunction with thinner n-ZnO layer. The photosensitivity (135) of the heterojunction with 180-nm n-ZnO layer is higher than that (79) of 60-nm n-ZnO layer. An energy band diagram was proposed to analyze I–V characteristics of the heterojunction.