Recent advances in Ga1−xInxSb/InAs superlattice IR detector materials

Development of Ga 1-x In X Sb/InAs superlattices has been motivated by potential applications to infrared (IR) detectors in the 8-12 μm band and the far IR region 12-20 + μm. Theoretical and experimental results to date support the prospect that very high performance III-V materials-based IR focal plane array (FPA) sensors that can operate at temperatures higher than HgCdTe photovoltaic devices are feasible. The heterostructures under development are grown by molecular beam epitaxy (MBE) and are type-II, broken gap superlattices of alternating layers of Ga 1-x In x Sb/InAs with compositions chosen to allow the superlattice to be symmetrically strained to GaSb substrates. The details of the interface structure at the GaSb surface, the character of the interfaces between the Ga 1-x In X Sb and InAs layers, and the chemical nature of the Group V flux used in the MBE growth process are among the critical factors in enabling the growth of superlattices of extremely high optical quality suitable for IR detectors. We review recent advances in the materials and epitaxial processes for growing these superlattices. These processes have been applied to producing IR detector structures tailored to the particularly difficult spectral range of very long wavelength cut-off of 12 + μm.