This project will investigate the fabrication of high-performance InSb detector arrays by molecular beam epitaxy (MBE) on GaAs. this effort will first develop two strained superlattices (SSL) in tandem for a near-perfect lattice match between the InSb and GaAs, and then fabricate the p-n junction for the 3-5 micron spectral region. The superlattice buffer will serve to block misfit dislocations from propagating into the InSb. The epitaxy of the n-type and p-type epilayers will be made in tandem by in-situ doping to form the p-n junction detectors.