All-Semiconductor Plasmonic Resonant Structure with Mid-Wave and Long Wave Infrared Enhancement

Multi-color infrared detectors are widely used in military, meteorological and other fields. Simultaneous enhancement of multiple wavelength in multi-color detectors is still a great challenge. A dual-band enhanced plasmonic type-II superlattice structure with a metal-dielectric-metal (MIM) cavity and cross-shaped hollow ellipses is designed and analyzed in this paper. Simultaneous enhancement of mid-wave infrared (MWIR) and long wave infrared (LWIR) wavelength can be realized. The cylindrical MIM cavity effectively reduces the reflectance of incident light on the detector surface in the mid-wave and long-wave spectrum, thereby increasing the detector's absorption and quantum efficiency. The thick metallic micro-structures are utilized for better impedance matching and form multiple resonant absorption. Besides, the detector uses heavily doped InAs instead of traditional metals to form an all-semiconductor plasmonic MIM cavity, which has better compatibility with the present fabricating process of detectors. The width of the absorption spectrum can also be modulated by varying the thickness of the InAs layer, realizing broadband absorption enhancement. The designed structure was systematically studied by the finite element simulation software COMSOL. The mechanism of double absorption enhancement was analyzed and the influences of key parameters, such as the thickness of heavily doped InAs, the period of the micro-structures and the incidence angle of light were discussed. The results show that the structure can realize significant enhancement of infrared detection in both MWIR and LWIR spectrum and the absorption is increased from 40% to 90% compared to a reference device without surface micro-structures. This approach provides a new way to design more effective dual-band IR detectors and promote the development of multi-color infrared detectors.