Dark Current Reduction and Performance Improvements in Graphene/Silicon Heterojunction Photodetectors Obtained Using a Non-Stoichiometric HfOx Thin Oxide Layer

Graphene/silicon heterojunction photodetectors suffer from a high dark current due to the high surface states and low barrier height at the interface, which limits their application. In this study, we introduce an HfOx interfacial layer via magnetron sputtering to address this issue. With this new structure, the dark current is reduced by six times under a bias voltage of −2 V. Under 460 nm illumination, the responsivity is 0.228A/W, the detectivity is 1.15 × 1011 cmHz1/2W−1, and the noise equivalent power is 8.75 × 10−5 pW/Hz1/2, demonstrating an excellent weak light detection capability. Additionally, the oxygen vacancies in the HfOx interfacial layer provide a conductive channel for charge carriers, resulting in a 2.03-fold increase in photocurrent and an external quantum efficiency of 76.5%. The photodetector maintains good photoresponse ability at a low bias voltage. This work showcases the outstanding performance of HfOx films as interfacial layer materials and provides a new solution for high-performance photodetectors, as well as a new path to improve the photovoltaic conversion efficiency of solar cells.