Infrared Proximity Sensors Based on Photo-Induced Tunneling in van der Waals Integration

Abstract

© 2021 Wiley-VCH GmbHInfrared (IR) detectors based on photo-induced tunneling in van der Waals heterostructures (vdWHs) of graphene/h-BN/graphene or MoS2/h-BN/graphene exhibit extremely low dark currents owing to a large electron barrier. However, a lack of tunneling barrier materials except for h-BN for 2D vdWHs limits their further enhancement. In this study, a broadband detection is reported with high sensitivity and fast photoresponse of IR proximity sensor by a vdW integration (2D-3D) of graphene or MoS2, with NiO/Ni as the IR absorber and hole selective transport layer/counter electrode. The low Schottky barrier height of the reported junctions suppresses dark current with a high detectivity ≈1014 Jones and generates a photocurrent by transporting photo-excited carriers through a low hole barrier at a wide wavelength. Two types of integrated IR proximity sensor applications are developed: a passive sensor (MoS2/NiO/Ni) for the near-IR (NIR) range and an active sensor (Gr/NiO/Ni) for the mid-IR (MIR) range. The former shows a broadband photoresponse to reflect the NIR, while the latter absorbs human body irradiation (2–16 µm wavelength) with a fast photoresponse of 3.5 s (rise time) and 1.8 s (fall time). The fabricated sensors utilize low power, broadband detection, high sensitivity, fast photoresponse, and large-scale area at room temperature.