  Taking into account the available experimental results, we model the
electronic properties and current-voltage characteristics of a
ferromagnet-semiconductor junction. The Fe/GaAs interface is considered as a
Fe/(i-GaAs)/n+-GaAs/n-GaAs multilayer structure with the Schottky barrier. We
also calculate numerically the current-voltage characteristics of a
double-Schottky-barrier structure Fe/GaAs/Fe, which are in agreement with
available experimental data. For this structure, we have estimated the spin
current in the GaAs layer, which characterizes spin injection from the
ferromagnet to the semiconductor.
