Visible-blind ultraviolet photodetector based on double heterojunction of n-ZnO/insulator-MgO∕p-Si

Exploiting a double heterojunction of n-ZnO/insulator-MgO∕p-Si grown by molecular beam epitaxy, a visible-blind ultraviolet (UV) photodetector has been fabricated. The photodetector shows a rectification ratio of ∼104 at ±2V and a dark current of 0.5nA at a reverse bias of −2V.The photoresponse spectrum indicates a visible-blind UV detectivity of our devices with a sharp cut off at the wavelength of 378nm and a high UV/visible rejection ratio. The key role of the middle insulating MgO layer, as a barrier layer for minority carrier transport, has been demonstrated.