High-Performance Self-Powered Gr/MoS2/WSe2 Heterojunction Photodetector Based on Asymmetric Van Der Waals Contacts.

Heterostructures based on transition metal dichalcogenides have shown considerable promise for self-powered photodetectors owing to their strong light-matter interaction and rapid interfacial charge transfer. However, the barrier at the semiconductor/metal interface can hinder efficient carrier transport. Therefore, reducing the Schottky barrier at the semiconductor/metal interface or utilizing the associated built-in electric field is important for improving device performance. In this study, a self-powered Gr/MoS2/WSe2 heterojunction photodetector based on asymmetric van der Waals (vdW) contacts was constructed, in which graphene is introduced as a transparent electrode to improve the contact characteristics of the MoS2/Au interface. Benefiting from carrier regulation by the asymmetric barriers at the Gr/MoS2 and WSe2/Au interfaces, as well as the built-in electric fields with the same direction at the MoS2/WSe2 and WSe2/Au interfaces, the device exhibits rise/fall times of 22/58 μs and a low dark current of 5.54 × 10-13 A. Under self-powered operation, the device exhibits a responsivity of 367 mA/W, an on/off ratio exceeding 106, and photodetection spanning the visible and near-infrared regions. In addition, demonstrations of imaging and near-infrared optical communication further indicate the potential of this heterojunction photodetector for optoelectronic applications.