Long Wavelength Type II Superlattice Barrier Infrared Detector for Cubsat Hyperspectral Thermal Imager

The hyperspectral thermal imaging instrument for technology demonstration funded by NASA’s Earth Science Technology Office under the In-Space Validation of Earth Science Technologies (InVEST) program requires focal plane array with superior performance at a low cost. The instrument is designed to fit in a 6U CubeSat planform for a low-Earth orbit. It will collect data on hydrological parameters and Earth surface temperature for agricultural remote sensing. The Long-Wavelength Infrared Type II Strain Layer Superlatice Barrier Infrared Detector focal plane array is chosen for this mission. With the driving requirement dictated by the power consumption of the cryocooler and Signal-Noise-Ratio, cutoff wavelengths and dark current are utilized to model instrument operating temperature. Many focal plane arrays are fabricated, characterized and the best performing FPA that fulfills the requirement is selected. The spectral band, dark current and 8-9.4 m pass band quantum efficiency of candidate FPA are 8-10.7m, 2.1x10-5 A/cm2 and 47 % respectively. The corresponding Noise Equivalent Difference Temperature and operability are 30 mK and 99.7% respectively. These parameters are within the requirement. Anti-Reflective coating is deposited on the focal plane array surface to enhance the quantum efficiency and to reduce the interference pattern due to absorption layer’s parallel surfaces cladding material.