InAs/GaInSb Superlattice for Very Long Wavelength Infrared Applications

GaInSb/InAs superlattices show great promise as materials for use in very long wavelength infrared (VLWIR) detectors. This III-V compound offers advantages over current HgCdTe technology in both anticipated performance level and ancillary support system(e.g. cryogenic cooling) costs. Due to its piezoelectric characteristic, (111)-oriented superlattice lowers the effective bandgap energy when compared to the same structure on (100), thereby more easily extending the operating wavelength into the VLWIRregime. However, growth on (111) substrates is known to be very challenging. During Phase I, we have demonstrated the growth of (111) superlattices, and identified problems associated with growth difficulties. We believe the material problems could besolved by employing the Engineered Substrate concept proposed for Phase II investigation. The compliant nature of such substrates will be able to accommodate the strain in the superlattice structure, and promote smooth 2-D epitaxy and sharp interfaces.Therefore we will be able to address the fundamental material issues and the work should lead to high performance VLWIR materials and devices.