Black phosphorus (BP) has emerged as a promising materials system for mid-wave infrared photodetection because of its moderate bandgap, high carrier mobility, substrate compatibility, and bandgap tunability. However, its uniquely tunable bandgap can only be taken advantage of with thin layer thicknesses, which ultimately limits the optical absorption of a BP photodetector. This work demonstrates an absorption-boosting resonant metal-insulator-metal (MIM) metasurface grating integrated with a thin-film BP photodetector. We designed and fabricated different MIM gratings and characterized their spectral properties. Then, we show that an MIM structure increased room temperature responsivity from 12 to 77 mA W-1 at 3.37 μm when integrated with a thin-film BP photodetector. Our results show that MIM structures simultaneously increase mid-wave infrared absorption and responsivity in a thin-film BP photodetector.
Keywords: Infrared photodetectors; black phosphorus; layered materials; light trapping.