Near-infrared graphene photodetector enabled by plasmonic hot carrier injection from disordered percolated gold nanostructures

Near-infrared graphene photodetectors are attractive for imaging, sensing, communication, and integrated optoelectronics, but their performance is strongly limited by the weak light absorption of graphene. Plasmonic nanostructures can enhance light-matter interaction; however, most reported devices rely on complex nano/microfabrication processes, which increases cost and limits scalability. Here, we demonstrate a near-infrared graphene photodetector enhanced by disordered percolated Au nanostructures through a simple fabrication process. The disordered Au nanostructures support broadband plasmonic absorption over 1200-1600 nm, producing strong local electromagnetic fields and facilitating hot-carrier generation. Spatially resolved photocurrent mapping, illumination-dependent transfer characteristics, and electromagnetic simulations support plasmon-induced hot-carrier injection from the Au nanostructures into graphene as an important contribution to the observed photoresponse. The resulting photoinduced carrier redistribution creates a potential difference between the Au-covered and uncovered graphene regions, providing the internal driving force for carrier transport at zero source-drain bias. The device exhibits a broadband zero-bias photoresponse over 1200-1600 nm, with a maximum voltage responsivity of approximately 20 mV/W. This work provides a simple and scalable route for low-cost plasmon-enhanced graphene near-infrared photodetectors.