Trap assisted charge multiplication enhanced photoresponse of Li–P codopedp-ZnO/n-Si heterojunction ultraviolet photodetectors

Abstract

In this work, we report a high-performance p-ZnO/n-Si heterojunction-based ultraviolet (UV) photodetector fabricated by dual ion beam sputter deposition. The lithium–phosphorus (Li–P) codoping route was used to realize low resistive and stable p-type ZnO. The current–voltage characteristics of p-ZnO/n-Si heterojunction photodiode showed good rectifying behavior with a rectification ratio of 170 at ±3 V. The spectral response measurements of the photodiode showed excellent responsivity with a peak observed around ~325 nm and cutoff wavelength around 370 nm. The maximum responsivity achieved was 2.6 A W−1 at an applied reverse bias of −6 V. The external quantum efficiency determined was of the order of ~1000% which is attributed to the trap assisted multiplication of charge carriers.