Highly spin-polarized room-temperature tunnel injector for semiconductor spintronics using MgO(100).

AlGaAs quantum well detectors. The polarizationreaches 57% at 100 K and 47% at 290 K in a 5 T perpendicular magnetic field. Taking into account thefield dependence of the luminescence polarization, the spin injection efficiency is at least 52% at 100 K,and 32% at 290 K. We find a nonmonotonic temperature dependence of the polarization which can beattributed to spin relaxation in the quantum well detectors.