Inverse-designed multi-diameter InAs nanowire array ultra-broadband photodetectors enhanced by localized surface plasmon resonances

Multi-diameter InAs nanowire array ultra-broadband photodetectors are inversely designed and further enhanced by localized surface plasmon resonances. The nanowire diameters are carefully selected by the particle swarm optimization algorithm within the range of 100-800 nm. The multi-diameter nanowire array exhibits high absorption over 80% within a broadband wavelength range of 0.5-3.42 µm, much wider and flatter than that of the single-diameter counterpart, which is attibuted to the superposition of multiple absorption peaks as well as the extension of absorption to longer wavelengths. By introducing indium tin oxide nanoparticles onto the nanowire surface, the lowest absorption is further raised to 87% within a broad wavelength range of 0.55-3.5 µm due to the localized surface plasmon resonances, and the dark current density is substantially reduced from 214 mA/cm to 83 mA/cm due to the large depletion region. This work may pave the way for the development of ultra-broadband high-responsivity infrared photodetectors.