Ultra-sensitive graphene photodetector with plasmonic structure

Abstract

We report a graphene-based photodetector with ultra-high photoresponsivity and wavelength selectivity, targeting at the mid-infrared (MIR) regime. To enhance the spectral selectivity, a gold-grating structure is designed and implemented under the graphene layer to excite surface plasmon polaritons (SPPs). The electromagnetic field with specific wavelength can be guided to and confined within the designed subwavelength structures. The graphene layer contacted by metal is slightly p-type doped due to gold grating, improving the interband transition rate of electrons. The built-in potential established in the contact region facilitates the separation of non-equilibrium carriers generated on graphene layer, leading to a photovoltage. With optimized structural design the photodetector exhibits excellent photoresponsivity of 1 V/μW at the wavelength of 9 μm.