Oxides/graphene heterostructure for deep-ultraviolet photovoltaic photodetector

Compared with photoconductive photodetectors (PDs), photovoltaic PDs not only have higher response speed and stability in theory, but also have the advantage of operating under zero bias. However, the current research of MgZnO (MZO) based deep-ultraviolet (DUV) PD is still mainly based on photoconductive PD. The reason for this situation is the lack of a conductive window layer that is unobstructed for DUV light in the vertical structure of the photovoltaic PD. In this work, a high-quality single hexagonal MZO thin film was grown on 4H-SiC substrate by magnetron sputtering, and the first vertical-structure (Gr/MZO/4H-SiC) DUV photovoltaic PD based on Gr/MZO van der Waals heterojunction was constructed by utilizing the single-layer graphene (Gr) which is high transmittance to DUV light. The device exhibited good photovoltaic response characteristics. Under 255 nm DUV light, the device had a stable open circuit voltage of 184 mV. Under zero bias, the photoresponsivity of the device is 2.64 mA/W, and the external quantum efficiency is 1.29%. While the response rise time is 0.0782 s, the decay time is 0.162 s, and the photoresponse cut off edge is 302 nm. More importantly, this result provides a new reference method for the development of high-performance MZO-based photovoltaic PD. (C) 2019 Elsevier Ltd. All rights reserved.