Complete spin polarization of degenerate electrons in semiconductors near ferromagnetic contacts

Abstract

We show that spin polarization of electron density in nonmagnetic degenerate semiconductors can achieve 100%. This effect is realized in ferromagnet-semiconductor $FM-n^{+}$-$n$ junctions even at moderate spin selectivity of the $FM-n^{+}$ contact when the electrons are extracted from the heavily doped $n^{+}-$semiconductor into the ferromagnet. We derived a general equation relating spin polarization of the current to that of the electron density in nonmagnetic semiconductors. We found that the effect of the complete spin polarization is achieved near $n^{+}$-$n$ interface when an effective diffusion coefficient goes to zero in this region while the diffusion current remains finite.