Beating the Responsivity‐Speed Trade‐Off in Asymmetric GaN‐Based UV Photodetectors: A Novel van der Waals Metal Contact Approach

Abstract Asymmetric‐type UV photodetectors have attracted extensive interest for their applications in modern optoelectronics. Conventional fabrication approaches for asymmetric metal contacts typically cause damage at the metal‐semiconductor interface, leading to Fermi level pinning and further limiting barrier height adjustability and functionality. Herein, for the first time, van der Waals (vdW) asymmetric metal contact on wide bandgap semiconductor gallium‐nitride (GaN) is successfully fabricated and achieve the mitigation of Fermi level pinning effect through the formation of a damage‐free metal‐semiconductor interface. Scanning transmission electron microscopy reveals an atomically clean and sharp interface with a distinct vdW gap between the semiconductor and metal electrode. More importantly, the absence of interface damage effectively suppresses charge recombination and results in substantial enhancement in photoresponse characteristics, demonstrating an increased responsivity from 1.8 to 56.7 A W −1 along with a significantly improved response/recovery time from 545/115 to 420/20 ms and an ultralow dark current at the picoampere‐level compared to that of the photodetector with electrodes fabricated with traditional e‐beam evaporated technique. Such simultaneously enhanced responsivity and response speed overcome the responsivity‐speed trade‐off in asymmetric photodetectors and mark a milestone in integrating asymmetric metal contacts with semiconductors through a non‐destructive manner, offering unparalleled opportunities for developing high‐performance asymmetric optoelectronic systems.