Heterostructured graphene quantum dot/WSe₂/Si photodetector with suppressed dark current and improved detectivity

A high-performance heterojunction photodetector is formed by combining an n-type Si substrate with p-type monolayer WSe₂ obtained using physical vapor deposition. The high quality of the WSe₂/Si heterojunction is demonstrated by the suppressed dark current of 1 nA and the extremely high rectification ratio of 10⁷. Under illumination, the heterojunction exhibits a wide photoresponse range from ultraviolet to near-infrared radiation. The introduction of graphene quantum dots (GQDs) greatly elevates the photodetective capabilities of the heterojunction with strong light absorption and long carrier lifetimes. The GQDs/WSe₂/Si heterojunction exhibits a high responsivity of ~ 707 mA·W^–1, short response time of 0.2 ms, and good specific detectivity of ~ 4.51 × 10⁹ Jones. These properties suggest that the GQDs/WSe₂/Si heterojunction holds great potential for application in future high-performance photodetectors.