  We report electrical spin injection from a ferromagnetic metal contact into a
semiconductor light emitting diode structure with an injection efficiency of
30% which persists to room temperature. The Schottky barrier formed at the
Fe/AlGaAs interface provides a natural tunnel barrier for injection of spin
polarized electrons under reverse bias. These carriers radiatively recombine,
emitting circularly polarized light, and the quantum selection rules relating
the optical and carrier spin polarizations provide a quantitative,
model-independent measure of injection efficiency. This demonstrates that spin
injecting contacts can be formed using a widely employed contact methodology,
providing a ready pathway for the integration of spin transport into
semiconductor processing technology.
