Electron spin polarizations of 32% are obtained in a GaAs quantum well via electrical injection through a reverse-biased Fe/AlGaAs Schottky contact. An analysis of the transport data using the Rowell criteria demonstrates that single step tunneling is the dominant transport mechanism. The current-voltage data show a clear zero-bias anomaly and phonon signatures corresponding to the GaAs-like and AlAs-like longitudinal-optical phonon modes of the AlGaAs barrier, providing further evidence for tunneling. These results provide experimental confirmation of several theoretical analyses indicating that tunneling enables significant spin injection from a metal into a semiconductor.
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