Spin polarized tunneling in III–V-based heterostructures with a ferromagnetic MnAs thin film and GaAs:MnAs nanoclusters

We have successfully fabricated epitaxial single-crystal magnetic tunnel junctions (MTJs) consisting of magnetic electrodes (ferromagnetic MnAs and GaAs:MnAs granular material) and a AlAs/GaAs III–V tunnel barrier, grown by molecular-beam epitaxy on GaAs(0 0 1) substrates. Clear tunneling magnetoresistance (TMR) was observed from 7 K up to room temperature. The bias voltage Vhalf at which the TMR ratio is reduced by half is 1200 mV at 7 K, which is surprisingly high and much higher than that (View the MathML source) of ferromagnetic semiconductor-based MTJs. This result shows that GaAs:MnAs nanoclusters can be used as a spin injecting source in semiconductor-based spintronics devices.