High-resolution QWIP FPAs for the 8-12 µm and 3-5 µm regimes

We report on our QWIP focal plane array (FPA) developments for the 8 - 12 µm and 3 - 5 µm regimes. In the long-wavelength infrared, we have realized several types of QWIP FPAs with array sizes from 256 x 256 to 640 x 512 pixels and with different active regions, giving rise to photoconductive and photovoltaic operation, respectively. Best thermal resolution in the 8 - 12 µm regime is obtained with low-noise QWIP FPAs which are based on a photovoltaic QWIP structure. Special emphasis is given to our work on a 640 x 512 mid-wave QWIP FPA, which is based on strained InGaAs/AIGaAs quantum wells lattice matched to a GaAs substrate. By optimizing the carrier concentration and the geometry of the two-dimensional grating with 1.65 µm period, a high quantum efficiency of more than 10% in the long-wavelength part of the 3 - 5 µm regime is achieved, resulting in an excellent thermal resolution of only 14.3 mK.