Spin-polarized tunneling through potential barriers at ferromagnetic metal/semiconductor Schottky contacts

A model for electron tunneling through a space-charge induced potential barrier at a semiconductor/ferromagnetic metal Schottky contact is developed and applied to the exploration of the bias dependence of the spin-polarized tunneling current. It is found that significant bias dependence of the spin polarization of the current can result from changes in the shape of the potential barrier due to the applied voltage. Specifically, we show that the dependence of the transmission coefficient on the shape of the barrier potential can lead to a nonmonotonic bias dependence of the spin current and may result in a reversal of the sign of the spin-current polarization at small voltages. Numerical results are presented for GaAs Fe Schottky contacts.