(Digital Presentation) The Photoresponse Enhancement of Graphene Photodetector By Metasurface Under Mid-Infrared Region

As a zero bandgap material, graphene has excellent optical properties and electrical doping characteristics. Graphene plasmons exhibit much larger confinement and longer propagation distances than noble-metal plasmons. The surface plasmons technique has been widely used in photodetectors because it can couple light to the devices for signal detection. In this paper, we combine graphene with existing surface-plasmon-based devices and show that the photocurrent is twice as intrinsic graphene devices under the same infrared light source. Metasurface on graphene/SiO2 under infrared light will induce plasmon–phonon quasi-particle, which will decay into electron-hole pairs and phonons. The former increases the total transport current and dominates in the graphene lightly doping condition. The latter decreases the total transport current and dominates in the graphene highly doping condition. As a result, the responsivity can be tailored by Fermi-level tuning. We demonstrate that the responsivity of the metasurface graphene photodetector can reach the ~5e-4 A/W in the mid-infrared region. It's believed that the high responsivity and photoresponse modulation has promising and flexible application scenarios in photodetectors.