An Uncooled LWIR-Detector with LSPR Enhancement and Selective Narrow Absorption

An uncooled plasmonic infrared photodetector with selective narrow absorption band in long-wave-infrared was demonstrated. The hydrogenated amorphous silicon (a-Si:H) with high temperature coefficient of resistance characteristic was adopted as a detection layer in the plasmonic photodetector. A tri-layer gold/a-Si:H/gold arrangement with metallic gold strip was designed to sustain localized surface plasmon resonances (LSPRs). By altering the metallic linewidth and the dielectric thickness, the LSPRs can be adjusted freely. Therefore, the incoming infrared with specific wavelength corresponding to LSPRs will heat up the cavity directly, leading to the reduction of a-Si:H resistance along the current path and the signal would be detected. The optical and electrical characteristics of the photodetector were studied. The responsivity and perpendicular photoresponse ratio without suspended structure was enhanced by LSP resonances and directly heat up process.