Ultra‐Fast Weak Light Detectors Based on van der Waals Stacked 2D Semiconductor/h‐BN Heterostructures

Abstract Fast and sensitive detectors for weak light are crucial in various fields like real‐time monitoring, medical diagnosis, and astronomy. However, photodetectors using 2D materials face challenges in achieving both a low detection limit for weak light and fast response. Here, a vertical vdW graphene/indium selenide (InSe)/hexagonal boron nitride (h‐BN) heterostructure on a gold electrode is provided, demonstrating an ultra‐low detection limit of 47.4 nW cm −2 and an ultra‐fast response speed of 327 ns. Vertical photodetectors feature nanoscale channel length, thus reducing scattering and recombination of carriers. The high potential barrier of multilayer h‐BN effectively blocks carrier transport, resulting in ultra‐low dark current and minimal power dissipation. Additionally, enhanced light absorption in InSe by the metal‐insulator‐semiconductor structure improves the sensitivity to weak light detection. More importantly, the built‐in field at the graphene/InSe interface can promote the separation of photo‐generated carriers to improve the collection efficiency. These factors jointly reduce the detection limit and response time simultaneously for weak light. This vertical vdW heterostructure comprising a 2D semiconductor/h‐BN offers a solution to make the majority of 2D semiconductors applicable in ultra‐fast weak light detectors.