Optical Pumping in Ferromagnet-Semiconductor Heterostructures: Magneto-optics and Spin Transport, Isakovic, A.F.; Carr, D.M.; Strand, J.; Schultz, B.D.; Palmstrøm, C.J.; Crowell, P.A. Phys. Rev. B 2001, 64, 161304R

One of the major problems in spin-dependent transport is scattering at the interface between ferromagnetic metals and semiconductors. In fact, unambiguous evidence for spin injection into semiconductors has been found only in all-semiconductor systems. Work by MRSEC-supported graduate students David Carr (Palmstrøm) and Abdel Isakovic (Crowell) has demonstrated that in fact the metal-semiconductor interface is "permeable" to spin. The measurements have been the most definitive of this type to date, using quantum wells embedded in Schottky diodes as a localized source of spin. Polarization-dependent photocurrents up to 10% are observed when electrons in the ground state of the quantum well are resonantly excited. These results indicate that the ferromagnet-semiconductor interface may be much more transparent to spin than previously believed.

Schematic picture of spin transport from a semiconductor (everything but the grey region) into a ferromagnetic metal. The electron spin, shown in purple, is created in the semiconductor by optical pumping with circularly polarized light. It is swept into the ferromagnet by the large electric field near the interface.