Type-II strained-layer superlattice digital focal plane arrays for earth remote sensing instruments

Abstract

Long-wavelength infrared (LWIR) focal plane arrays (FPAs) needed for Earth Science imaging, spectral imaging, and sounding applications have always been among the most challenging in infrared photodetector technology due to the rigorous material growth, device design and fabrication demands. Future small satellite missions will present even more challenges for infrared FPAs, as operating temperature must be increased so that cooler (and radiator) volume, mass, and power can be reduced. To address this critical need, we are working on following three technologies. 1) Type-II superlattice (T2SL) nBn type barrier infrared detector, which combines the high operability, spatial uniformity, temporal stability, scalability, producibility, and affordability advantages of III-V detectors. 2) The resonator pixel technology, which uses metasurface light trapping techniques to achieve strong absorption in a small detector absorber volume, thereby enabling enhanced QE and/or reduced dark current. 3) High dynamic range 3D Readout IC (3D-ROIC), which integrates a digital reset counter with a conventional analog ROIC to provide a much higher effective well capacity than previously achievable. The resulting longer integration times are especially beneficial for high flux/dark current LWIR applications as they can improve signal-to-noise ratio and/or increase the operating temperature. By combining these three technologies, this project seeks to demonstrate a cost-effective, high performance LWIR FPA technology with significantly higher operating temperature and sensitivity than previously attainable, and with the flexibility to meet a variety of Earth Science TIR measurement needs, particularly the special requirements of small satellite missions.