UV-detector based on pn-heterojunction diode composed of transparent oxide semiconductors, p-NiO/n-ZnO

A transparent ultraviolet (UV)-detector was fabricated using a high-quality pn-heterojunction diode composed of transparent oxide semiconductors, p-type NiO and n-type ZnO, and its UV-response was measured at room temperature. Transparent tri-layered oxide films of ZnO/NiO/ITO were heteroepitaxially grown on an YSZ (1 1 1) substrate by a pulsed-laser-deposition combined with a solid-phase-epitaxy technique and they were processed to fabricate a p-NiO/n-ZnO diode. The diodes exhibited a clear rectifying I– V characteristic with an ideality factor of ∼2 and a forward threshold voltage of ∼1 V. Although the photo-responsivity was fairly weak at the zero bias voltage, it was enhanced up to ∼0.3 A W −1 by applying a reverse bias of −6 V under an irradiation of 360-nm light, which is comparable to that of commercial devices.