Potential barrier for spin-polarized electrons induced by the exchange interaction at the interface in the ferromagnet/semiconductor heterostructure.

We have calculated the exchange interaction between electrons in the accumulation electron layer in the semiconductor near the interface and electrons in the ferromagnet in the ferromagnet/semiconductor heterostructure. It is found that the exchange interaction forms the potential barrier for spin-polarized electrons. The barrier height strongly depends on the difference of chemical potentials between the semiconductor and the ferromagnet. The maximum of the potential barrier height on the temperature dependence is due to the existence of localized electron states in the accumulation layer. In the framework of the developed theoretical model, the injection magnetoresistance effect observed in semiconductor/granular film heterostructures with ferromagnetic metal nanoparticles is explained. A spin filter on the base of granular film/semiconductor/granular film heterostructures operated at room temperature is proposed.