We examined the electrical injection of spin-polarized electrons into a GaAs-based light-emitting diode structure from a Fe/GaOx tunnel injector whose electron-charge injection efficiency was comparable to that of a conventional Fe/n+-AlGaAs ohmic injector. A high circular polarization of electroluminescence up to 20% was observed at 2 K. The combination of effective spin-and charge-injection efficiencies makes GaOx a promising tunnel barrier for GaAs-based spintronic devices.
We fabricated Fe/GaO
x
/Fe magnetic tunnel junctions (MTJs) where GaO
x
is a wide-gap amorphous semiconductor. At room temperature, the MTJs showed magnetoresistance (MR) ratios up to 10% as well as high bias-voltage (V
half) of 500 mV, where the MR ratio becomes half the zero-bias value. It was found that the MTJ has a very low effective barrier height (φeff) of 0.17 eV which is one of the lowest values among the ever reported in MTJs. We proved that effective mass of tunneling electron in GaO
x
is only 11% of free electron mass, which plays a crucial role on the observed low φeff.
We investigated the effect of thin GaOx insertion layers on the Schottky barrier height ϕB for Fe/n-GaAs junctions. The value of ϕB showed a remarkable decrease from 0.84 down to 0.56 eV with increasing GaOx thickness up to 2.0 nm. Large suppression of ϕB is of greater advantage than using other oxide materials for achieving low contact resistance of the emitter/detector electrodes, which is the key to developing high-performance GaAs-based spintronics devices.
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