All-van-der-Waals Heterostructure of MoS Grating and InSe Flake for Spectrally Selective Polarization-Sensitive Photodetection in NIR Region.

Near-infrared (NIR) polarization photodetectors based on 2D materials hold immense potential for numerous optoelectronic applications. To enhance the weak light-matter interaction in 2D materials, integrating 2D semiconductors with metallic plasmonic nanostructures presents an effective solution. However, such metallic plasmonic nanostructures suffer from high optical loss in the infrared region owing to inherent Ohmic losses in metals. By developing an all-van-der-Waals (vdW) heterostructure of MoS grating and InSe flake, we demonstrate a spectrally selective polarization-sensitive NIR photodetector. Herein, bulk MoS gratings possess lower optical loss and stronger field confinement compared to conventional metallic gratings, leading to a higher photoelectric conversion efficiency. Additionally, the MoS grating supports both TE-excited guided-mode resonance at λ = 790 nm and TM-excited plasmonic resonance at λ = 960 nm. Such linear dichroism conversion behavior, with wavelength tunability, enables spectrally selective polarization-sensitive photodetection in the NIR region, achieving high dichroic ratios of 1.61 at 790 nm and 1.88 at 960 nm. Under 960 nm illumination, such MoS grating/InSe flake photodetector also demonstrates a responsivity of 28.5 A/W and a detectivity of 9.81 × 10 Jones, respectively. In addition, with an ultrafast rise time of 195 ns and a decay time of 222 ns, this device represents the fastest photoresponse speed among InSe-based photodetectors reported to date. These results highlight the potential of 2D semiconductor gratings for high-performance all-vdW optoelectronics and nanophotonic devices.