High‐Performance van der Waals Metal‐Insulator‐Semiconductor Photodetector Optimized with Valence Band Matching

Abstract The vertical metal‐insulator‐semiconductor (MIS) photodetectors based on van der Waals heterostructures (vdWHs), fabricated by rationally stacking different layers without the limit of lattice‐match, have attracted broad interest due to their wide wavelength monitoring range, high responsivity, high detectivity, and fast response. Here, for the first time, the control of barrier height in vdWHs MIS photodetectors is systematically investigated. Optimizing semiconducting and insulating layers enables lowering the hole barrier height to achieve a high performance of the device. Graphene/hexagonal boron nitride (h‐BN)/SnS 2 device shows the best photodetection performance compared to the other common 2D semiconductors. The lowest barrier height ensures that the photo‐induced holes transfer efficiently to the graphene electrode and the dark current is highly suppressed by the h‐BN layers. Consequently, the graphene/h‐BN/SnS 2 MIS photodetectors have a high photoresponsivity of 2 A W −1 , a high detectivity of 10 13 Jones, and a photocurrent/dark current ratio of 5.2 × 10 5 at a low applied bias of −0.6 V. The highest detectivity reaches 9.6 × 10 13 Jones which is 100–1000 times greater than previously reported vdWHs MIS photodetectors.