Dark Current Reduction and Performance Improvements in Graphene/Silicon Heterojunction Photodetectors Obtained Using a Non-Stoichiometric HfO x 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 HfO x 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 × 10 11 cmHz 1/2 W -1 , and the noise equivalent power is 8.75 × 10 -5 pW/Hz 1/2 , demonstrating an excellent weak light detection capability. Additionally, the oxygen vacancies in the HfO x 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 HfO x 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.