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 ${\Lambda }_S\ge 4.6\mu \mathrm{m}$ and ${\tau }_s\ge 3.8\mathrm{ps}$, respectively. The temperature dependence is weak over the range $4.5<T<\mathrm{}150\mathrm{}\mathrm{K}$.