Detection of spin-polarized electrons injected into a two-dimensional electron gas

The spin-dependent mean-free path of electrons in a high-mobility InAs two-dimensional electron gas (2DEG) is measured. Ferromagnetic metal/insulator/2DEG junctions are fabricated on a common channel in a nonlocal geometry and used as spin injectors and detectors. For electrons in spin-orbit eigenstates at 4.5 K, lower bounds for the spin mean-free path and relaxation time are Lambda(S) > or = 4.6 microm and tau(s) > or = 3.8 ps, respectively. The temperature dependence is weak over the range 4.5