Ultrafast Self-Driven WSe₂ Photodetectors with Bottom Schottky Contacts

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/WSe₂/Au heterostructure. The key innovation involves fabricating the bottom Schottky Cr electrode into pre-etched SiO₂ 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/WSe₂ interface, mitigating Fermi-level pinning. Consequently, the device exhibits an outstanding rectification ratio of 1.07 × 10⁴ 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.