Ratan K. Debnath, Ting Xie, Baomei Wen, Wei Li, Abhishek Motayed, Nhan V. Nguyen
This paper presents a high efficiency heterojunction p-NiO/n-ZnO thin film ultraviolent (UV) photodetector fabricated on conductive glass substrates. The devices are fabricated by using a simple spin-coating layer-by-layer method from precursor solutions. Photodiodes show good photoresponse and quantum efficiency under UV illumination. With an applied reverse bias of 1 V, the devices show maximum responsivity and detectivity of 0.28 A/W and 6.3 x 1011 Jones, respectively, as well as high gain with external quantum efficiency (EQE) of over 90%. We have also fabricated photodetectors (PDs) utilizing ultrathin Ti/Au as top UV transparent metal contacts that can be illuminated either through glass or metal side. Laser beam induced current is used to examine the local variation of EQE providing information on the photoresponse behavior within the device. Optical properties of NiO and ZnO deposits have also been explored.