Long wavelength type-II superlattice barrier infrared detector for CubeSat hyperspectral thermal imager

Abstract

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 program requires focal plane array with reasonably good performance at a low cost. The instrument is designed to fit in a 6U CubeSat platform 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 superlattices 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, cut-off wavelengths and dark current are utilized to model instrument operating temperature. Many focal plane arrays are fabricated and characterised, and the best performing focal plane array that fulfils the requirements is selected. The spectral band, dark current and 8-9.4 m pass band quantum efficiency of the candidate focal plane array are: 8-10.7 m, 2.1•10 −5 A/cm 2 , and 47%, respectively. The corresponding noise equivalent difference temperature and operability are 30 mK and 99.7%, respectively. Anti-reflective coating is deposited on the focal plane array surface to enhance the quantum efficiency and to reduce the interference pattern due to an absorption layer parallel surfaces cladding material.

Rigorous optical modelling of long-wavelength infrared photodetector with 2D subwavelength hole array in gold film

“…The InAs/InAsSb type-II superlattice (T2SL) was chosen as an active material because its band gap and corresponding cut-off wavelength may be easily tuned in a wide range between 4 µm and 16 µm by changing the superlattice period and the InAs/InAsSb layer thickness ratio while the InAsSb composition adjustment enables balancing strain in the structure [10][11][12]. Another advantage of this material compared to bulk InAsSb is lower Shockley-Read-Hall recombination due to reduced defect density.…”