Gate-Tunable Rectifiers and Self-Powered Photodetectors Based on TaS 2 /WSe 2 /Bi Asymmetrical Schottky Junction

Asymmetrical contact engineering has emerged as an efficient strategy for realizing high-performance Schottky junction-dependent rectifiers and self-powered photodetectors based on two-dimensional (2D) materials, which is of great significance for a new generation of low-power electronic and optoelectronic devices. However, conventional evaporated-metal electrodes frequently induce pronounced Fermi-level pinning at the 2D semiconductor-metal interface, rendering the Schottky barrier height (SBH) insensitive to the metal work-function difference and thereby precluding the deliberate formation of asymmetrical Schottky barriers through metal selection alone. Herein, we report a Schottky junction-based multilayer WSe₂ with asymmetrical Fermi-level pinning-free contacts integrated with metallic 2D van der Waals (vdW)-stacked 2H-TaS₂ and low-melting-point semimetallic Bi electrodes that preserves the metal work-function difference effectively owing to the damage-free and atomic-clean interface, which can function simultaneously as a rectifier and a self-powered photodetector. Employing a high-work-function TaS₂-contacted electrode helps to facilitate hole-dominated p-type transport, whereas low-work-function Bi forms an almost ideal ohmic n-type contact with an extremely low electron Schottky barrier. Owing to the gate-tunable Fermi level of WSe₂ and SBH, the device exhibits rectifying output characteristics at various gate voltages, and the rectification ratio increases as the voltage rises from 1 × 10² to 1 × 10⁴. Moreover, the responsivity of the self-powered photodetector presents 17.86 and 340.7 A/W under gate voltages of -60 and 60 V, respectively, all achieved under zero-bias conditions. The device also enables low dark current and demonstrates exceptional illumination switching reliability, with switching ratios of 1 × 10⁴ and 1 × 10⁶ at the respective gate voltages. This work presents a novel approach for developing superior-performance rectifiers and energy-efficient, low-power-consuming adaptive photodetectors.