Photo-driven all-2D van der Waals metal–semiconductor field-effect transistors for high-performance photodetection

Abstract

Photodetectors based on 2D materials have garnered significant attention due to their remarkable performance characteristics. However, widely adopted photodiodes and photoconductors typically face challenges in achieving both high responsivity and fast response speed. Here, a photovoltage-driven metal–semiconductor field-effect transistor (photo-MESFET) is proposed, utilizing 2D metallic 2H-NbSe₂ as the top-gate electrode and n-type semiconductor MoS₂ as the channel material. Owing to the high-quality Schottky contact between NbSe₂ and MoS₂, the MESFET exhibits a low subthreshold swing of ∼79 mV dec⁻¹ and a high on/off ratio of ∼10⁶. Additionally, the device demonstrates an extremely low dark current of ∼2.9 pA with a top-gate bias of −0.5 V, attributed to the complete depletion of the channel. Under 650 nm laser illumination, the photogenerated voltage at the NbSe₂/MoS₂ heterointerface effectively modulates the depletion region and conductivity in the MoS₂ channel, which enables the device to achieve concurrent optimization with a high responsivity of ∼9.56 A W⁻¹ and a fast response time of ∼206 μs. Accordingly, the photo-MESFET also attains a high specific detectivity of ∼2.23 × 10¹⁰ Jones and a large I_on/I_off ratio of ∼4.1 × 10⁵, demonstrating excellent imaging capabilities. The photo-MESFET offers a viable solution for realizing comprehensive high-performance photodetectors.