Infrared Photodetector Based on the Photothermionic Effect of Graphene-Nanowall/Silicon Heterojunction

Because of the slow relaxation process according to weak acoustic phonon interaction, the photothermionic effect in graphene could be much more obvious than in the metal film, so a graphene heterojunction photodetector based on the photothermionic effect is promising for infrared imaging applications. However, the 2.3% absorption rate of the graphene film presents a severe limitation. Here, in situ grown graphene nanowalls (GNWs) were integrated on the silicon substrate interfaced with Au nanoparticles. Because of the strong infrared absorption and hot-carrier relaxation process in GNWs, the as-prepared GNWs/Au/silicon heterojunction has a photo to dark ratio of 2 × 104, responsivity of 138 mA/W, and linear dynamic range of 89.7 dB, with a specific detectivity of 1.4 × 1010 and 1.6 × 109 cm Hz1/2/W based on calculated and measured noise, respectively, in 1550 nm at room temperature, and has the best performance among silicon-compatible infrared photodetectors without any complicated waveguide structures. ...