Ultrafast Self‐Driven WSe ₂ Photodetectors with Bottom Schottky Contacts

Abstract Conventional top‐contact two dimensional (2D) Schottky photodetectors suffer from light shadowing and contact damage, leading to Fermi‐level pinning and performance degradation. This work overcomes these limitations by designing a bottom‐electrode Schottky photodetector (BE‐Schottky PD) based on a Cr/WSe ₂ /Au heterostructure. The key innovation involves fabricating the bottom Schottky Cr electrode into pre‐etched SiO ₂ substrate trenches, making it flush with the surface. This unique geometry eliminates optical shadowing to maximize light absorption, and enables a high‐quality van der Waals Cr/WSe ₂ interface, mitigating Fermi‐level pinning. Consequently, the device exhibits an outstanding rectification ratio of 1.07 × 10 ⁴ and an ideality factor of 1.11 due to the strong built‐in electric field. It demonstrates excellent self‐powered operation within the visible spectrum. Under 532 nm laser illumination and zero bias, it achieves rapid photoresponse with a fall time of 3.8 µs. This work, utilizing industry‐compatible metals and a simple process, realizes a high‐performance photodetector, highlighting the significant potential of 2D materials for efficient, low‐power, and ultrasensitive optoelectronics.