Feasibility Study of VLWIR InAs/GaSb Type-II Superlattice for Focal Plane Arrays.

High performance infrared detectors in the very long wavelength infrared (VLWIR) spectral bands are highly needed in a number of missile defense missions. The current state-of-the-art infrared detection technology for missile defense programs is based on the Mercury Cadmium Telluride (HgCdTe) compounds. However, at present it is becoming increasingly apparent that this detection technology is approaching the intrinsic physical limits of the material system. Type-II InAs/GaSb superlattices are expected to enable high performance next generation VLWIR focal plane arrays due to the intrinsic advantages of these materials. Type-II does not suffer from the same issue as HgCdTe when moving towards the VLWIR. In addition, owing to its coupled quantum well design, the cutoff wavelength across a typical 2” wafer is relatively insensitive to normal variations in layer thicknesses. Finally, the band structures of these superlattices can be engineered to suppress Auger recombination mechanisms for certain superlattice compositions, covering a wavelength range from 2 mm up to at least 32 mm. The overall goal of this work is demonstrating the feasibility of VLWIR detectors based on type-II InAs/GaSb superlattices detectors for focal plane array imaging. After demonstration, this technology can then be applied to the realization of VLWIR FPAs.