Ultrafast electron spin relaxation in 6.1-angstrom-lattice-constant semiconductors

Summary form only given. We describe ultrafast optical measurements of electron spin relaxation in InAs/GaSb superlattices with band gaps in the mid-infrared. Quantum structures comprised of semiconductors such as InAs and GaSb, with lattice constants of /spl sim/6.1-/spl Aring/, are currently being explored for application to a variety of advanced electronic and optoelectronic devices, including resonant-interband-tunneling diodes and mid-infrared lasers and detectors. The large spin-orbit coupling and interface asymmetry in these no-common-anion superlattices are expected to enhance the spin relaxation rates relative to, e.g., GaAs/Al(Ga)As heterostructures. We demonstrate that these factors lead to an unusual regime in which carrier spin relaxation occurs on a time scale comparable to energy relaxation.