Synergistic Impedance Matching and Plasmonic Enhancement in Graphene‐Quantum Well for Narrowband Mid‐Infrared Photodetection

Conventional quantum well infrared photodetectors (QWIPs) suffer from inherent limitations, including low scalability and insufficient narrowband absorption efficiency for specific spectral bands. This work proposes a structure of the coupled graphene‐quantum well photodetector that achieves highly efficient narrowband absorption at 6 μm through synergistic optimization of plasmonic resonance in metallic gratings and graphene‐enabled impedance matching. First, the plasma effect excited at the interface between graphene and the metal grating at the top of the detector is used to enhance optical coupling; second, the impedance matching effect of the graphene‐quantum well composite layer is used to reduce light reflection. At the same time, the high mobility characteristics of the graphene layer also promote the separation and transport of carriers. Under the combined effect of these effects, the absorptivity of the photodetector is greatly improved. The results demonstrate a peak absorption of 91.96% at 6 μm with a low reflection coefficient of −11.37 dB when the grating period is 200 nm. The absorption performance exhibits minimal sensitivity to incident angles within a wide range of 0° to 80°, highlighting high angular tolerance.