Tuning spin-current across a Semiconductor/Ferromagnet junction by resonance tunneling

We present a theory of spin-dependent transport in a hybrid semiconductor/ferromagnet system which includes an asymmetric double barrier region at the interface (e.g., GaAs/AlGaAs/GaAs/Fe). The system has two electron confinement regions with one being a thin quantum well between a heterostructure barrier and a Schottky barrier. The second confinement region is a two dimensional electron gas (2DEG) at the heterointerface with the bulk semiconductor generated by intentional doping. The I-V curve has two current peaks when electrons tunnel into the ferromagnet. These peaks are due to resonance tunneling of electrons whose energy matches the energy of the quasi-bound state in the quantum well. The first peak is governed by tunneling of delocalized electrons from the bulk semiconductor and the second by escape from the 2DEG. These resonances are met at different bias levels and correspond to opposite spin polarization of the current.