Black Phosphorus Molybdenum Disulfide Midwave Infrared Photodiodes with Broadband Absorption-Increasing Metasurfaces

Black phosphorus (BP) has been established as a promising material for room temperature midwave infrared (MWIR) photodetectors. However, many of its attractive optoelectronic properties are often observable only at smaller film thicknesses, which inhibits photodetector absorption and performance. In this work, we show that metasurface gratings increase the absorption of BP-MoS₂ heterojunction photodiodes over a broad range of wavelengths in the MWIR. We designed, fabricated, and characterized metasurface gratings that increase absorption at selected wavelengths or broad spectral ranges. We evaluated the broadband metasurfaces by measuring the room temperature responsivity and specific detectivity of BP-MoS₂ photodiodes at multiple MWIR wavelengths. Our results show that broadband metasurface gratings are a scalable approach for boosting the performance of BP photodiodes over large spectral ranges.