Spin polarization control through resonant states in an Fe/GaAs Schottky barrier

We show that \textit{the IRSs }\textit{(Interface Resonant States)}\textit{ within the Schottky barrier }play an important role for the negative spin polarization of the current and its bias dependence, and compare with our experimental results [1]. We have calculated the spin polarization $P$ of the tunnel conductivity using a full-orbital tight-binding model, and have shown that the IRSs within the Schottky barrier in the GaAs layer influence significantly the spin-dependent tunneling across the interface. It has been clearly shown that the band matching of the IRSs plays a crucial role on the spin polarization. The theoretical results account well for earlier experimental results including the tunneling of photo-excited electrons. The present results suggest that the spin polarization can be controlled by the Schottky barrier heights, and that a spin-switch device with bias control may also be promising. Quantitative performance of the device, however, needs more quantitative calculations including effects of atomic disorder for example. [1] H. Kurebayashi \textit{et al.}, \textit{Appl. Phys. Lett.} \textbf{91}, 102114 (2007).