Multispectral long-wavelength quantum-well infrared photodetectors

Multispectral detector arrays for application in the 8–11 μm spectral band have been fabricated from GaAs/AlGaAs multiple quantum-well (MQW) materials. For efficient narrow-band coupling of the infrared radiation, three-dimensional diffractive resonant optical cavities are patterned into the MQW material. The peak wavelengths of the multispectral quantum-well infrared photodetectors are tuned by controlling the dimensions of the resonant structure. The full width at half maximum of the spectral response is as narrow as 0.7 μm. As many as 24 different detector designs were implemented on a single array. The spectrally tuned detectors exhibit peak responsivities as high as 2.6 A/W and quantum efficiency as high as 57%. Total conversion efficiency is as high as 35%. The background limited peak detectivity measured at 9.0 μm and 55 K with a 295 K background and f/2.5 is ⩾1×1011 cm Hz0.5/W.