Enhanced Photodetection Performance in Graphene-Assisted Tunneling Photodetector

The vertical van der Waals heterostructures based on 2-D materials have attracted tremendous attention in optoelectronic devices as they can offer perfect interface without dangling bonds, atomic layer thicknesses, and conveniently tunable energy band alignment. However, the carrier transport mechanism in vertically stacked van der Waals heterostructure photodetectors is usually neglected in regards of photoresponse enhancement strategy, leading to low photoresponsivity and quantum efficiency. Here, we report a vertically stacked tunneling photodetector based on WSe2/graphene/WS2 van der Waals heterostructure. By introducing graphene film into the WSe2/WS2 interface, the interface composition was ameliorated and the Fowler–Nordheim tunneling (FNT) was enhanced with the reduced tunneling barrier height and thickness, caused by the elevated energy level of electrons since strong electron–electron interaction, ultrafast thermalization (~50 fs), and massless Dirac electrons of graphene. Therefore, the device exhibits a high photocurrent/dark current ratio (>104), fast response time ( $\sim 300~ \mu \text{s}$ ), high detectivity ( $\sim 1.58\times 10^{12}$ Jones), and high responsivity (429 mA W−1) across a broad spectral range till $1~ \mu \text{m}$ at room temperature. The optimized detectivity and responsivity are about 150 times and 50 times higher than WSe2/WS2 device without graphene, respectively. These results contribute to offer a novel and versatile strategy for overcoming the performance limitation in van der Waals photodetector.