Spin-polarized electron transport in ferromagnet/semiconductor hybrid structures induced by photon excitation

Circularly polarized light was used to excite electrons with a spin polarization perpendicular to the film plane in $3{\mathrm{nm}\mathrm{}\mathrm{A}\mathrm{u}/5\mathrm{}\mathrm{}\mathrm{nm}\mathrm{}\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}/\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}\mathrm{}\left(100\right)\mathrm{}$ structures with doping density in the range ${10}^{23}$ to ${10}^{25}{\mathrm{m}}^{\mathrm{-}3}.$ At negative bias a helicity-dependent photocurrent dependent upon the magnetization configuration of the film and the Schottky barrier height was detected. The helicity-dependent photocurrent polarization decreases with increasing doping density and has the same variation with photon energy as found for the polarization of photoexcited electrons in GaAs. The results provide unambiguous evidence of spin-dependent electron transport through the NiFe/GaAs interface and show that the Schottky barrier height controls the spin-dependent electron current passing from the semiconductor to the ferromagnet.