Photovoltaic characterization of graphene-GaN schottky junction in MESFET

Abstract

We present a photovoltaic regime high performance ultraviolet photodetector based on graphene-GaN Schottky junction in MESFET (Metal-Semiconductor Field Effect Transistor). A maximum responsivity of 36.9 A/W (EQE (External Quantum Efficiency) of 131.09×102%), and a photocurrent gain of 1.17×103 are obtained under 350 nm illumination at 0 V bias. The high response is attributed to the generation of significant forward voltage across the Schottky junction which in turn greatly contributes to the dark current opposing the photocurrent arising from drift and diffusion components. At −1.1 V reverse bias, the response is moderate (0.167 A/W) whereas at 1 V forward bias, the device shows zero photoresponse. The device also finds use in bias-selective multi-operation-mode with: a) Schottky junction operating as a photodetector at zero (gate and drain) bias and MESFET turned off; b) MESFET acting as an optically controlled device and Schottky photodetector turned off by appropriately choosing gate and drain biases; or c) MEFSET acting as an optically controlled device and Schottky junction acting as a photodetector simultaneously by suitably choosing gate and drain biases. The Schottky junction photovoltaic regime UV photodetector exhibits enhanced or comparable performance to numerous Schottky-based photodiodes mentioned in the literature. The device shows high potential for ultraviolet applications.