Tunneling-barrier-controlled sensitive deep ultraviolet photodetectors based on van der Waals heterostructures.

Abstract

Deep ultraviolet (DUV) photodetection usually relies on wide-bandgap semiconductors, which however face challenges in material growth and doping processes. In this work, we proposed and validated a photodetection scheme based on tunneling barrier modulation, achieving highly sensitive DUV photodetection. Using a two-dimensional van der Waals heterostructure, the device integrates MoS₂ as the transporting layer for its high carrier mobility and low dark current, few-layered graphene (FLG) as the photon absorption layer, and hexagonal boron nitride (hBN) as the dielectric barrier. The device exhibits an photoresponsivity of 4.4 × 10⁶A·W^-1 and specific detectivity of 1.4 × 10¹⁷ <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>cm</mi> <mo>⋅</mo> <msup><mrow><mi>H</mi> <mi>z</mi></mrow> <mrow><mo>-</mo> <mn>1</mn> <mo>/</mo> <mn>2</mn></mrow> </msup> <mo>⋅</mo> <msup><mrow><mi>W</mi></mrow> <mrow><mo>-</mo> <mn>1</mn></mrow> </msup> </math> for 250 nm DUV light, with a rejection ratio R₂₅₀/R₄₅₀ exceeding 10⁶ for visible light. Unlike conventional photodetectors, the cutoff wavelength is determined by the tunneling barrier rather than the material bandgap. Additionally, this photodetection scheme has been extended to a wide range of materials, utilizing different charge transporting layer (e.g., MoS₂, ReS₂), barrier layer (e.g., hBN, Al₂O₃), and photon absorption materials (e.g., FLG, PdSe₂, Au, Pd), showcasing its broad adaptability and potential for extensive application. Furthermore, the device has been successfully employed as a power meter for weak UV radiation (0.1 μW·cm^-2) and for measuring solar UV irradiance with results matching the meteorological agency's weather reports. Overall, this work introduces an effective approach for developing high-performance DUV photodetectors, highlighting significant potential for applications in the optoelectronic market.