Realizing Ultrafast Response Speed and High Responsivity for a Gate-Modulated All-2D Asymmetric Self-Powered Photodetector with Gr/MoS ₂ /NbSe ₂ van der Waals Heterostructure

Two-dimensional (2D) materials enable sensitive and fast self-powered devices based on van der Waals heterostructures. However, conventional 2D devices typically employ 3D metal electrodes, often resulting in Fermi-level pinning. Meanwhile, as limited interfacial band coupling restricts applications, gate-voltage modulation of the Fermi level has emerged as a promising strategy. In this study, we designed an all-2D asymmetric-contact photodetector capable of gate modulation, utilizing graphene (Gr) and NbSe₂ as electrodes for the 2D semiconductor MoS₂. Benefiting from the asymmetric built-in electric field, the device exhibits a maximum responsivity of 944.1 mA/W, ultrafast rise/decay time of 4/4 μs, a high 3 dB frequency of 10.2 kHz, and broad spectral response from visible to near-infrared light at zero bias. Furthermore, as the gate voltage increases from -40 to 40 V, the responsivity (<i>R</i>) rises from 478.8 to 1042.8 mA/W. This study highlights the potential of all-2D optoelectronic devices for high-performance near-infrared photodetection.