Plasmonic Metasurface Integrated Black Phosphorus-Based Mid-Infrared Photodetector with High Responsivity and Speed

Black Phosphorus (BP), a van der Waals (vdW) semiconducting material, is studied intensively due to its unique structural and anisotropic optical properties. BP exhibits optical anisotropy with thickness tunable direct bandgap from 0.3-2.0 eV. Many BP-based photodetectors operating in the mid-infrared (MIR) band are proposed, but their performance is still limited due to the small optical absorption cross section at room temperature. In this work, a plasmonic metasurface that has localized surface plasmon resonance (LSPR) at 3.7 mu m is designed, matching well with the band edge of a BP flake and field confinement around the edge of Au-disk as confirmed by finite difference time domain simulation and Fourier-transform infrared spectroscopy measurement results. In addition, a BP flake is integrated on the plasmonic metasurface and a significant quenching (twelve-fold) is observed in the photoluminescence owing to the Forster resonance energy transfer effect induced by dipole-dipole coupling. Following that, a BP-based MIR photodetector is fabricated on the plasmonic metasurface. Here, the demonstrated BP/plasmonic metasurface-based photodetector achieves the peak responsivity of 495.85 mAW(-1) and ultrahigh operation speed (>10 MHz) at the power of 8.55 mu W under 3.7 mu m incident wavelength. This demonstrated photodetector opens a new opportunity for optoelectronic applications in the MIR region.