Electrical injection of spin polarized electrons into GaAs

Electrical spin injection into semiconductors has been a challenge during the last years. Although many attempts have been made to realize spin injection from a ferromagnetic metal into a semiconductor two-dimensional electron gas (2DEG), all effects published up to now were small and could easily be explained by stray Hall effects or magnetoresistance. We have developed a theoretical model, which explains these negative results by the mismatch in conductivities and spin scattering in metallic ferromagnets and semiconductors. At the same time, the model indicates the direction towards more promising devices using highly spin polarized II-VI-magnetic semiconductors as a spin aligner. We have demonstrated highly efficient spin injection into a GaAs/ AlGaAs light emitting diode. The spin polarization was detected via the optical polarization of the emitted light.