Influence of Impurity Scattering on Spin Injection Efficiency at a Ferromagnet/Semiconductor Quantum Wire Interface

The influence of impurity scattering on the electrical spin injection efficiency from a non-ideal ferromagnet into a semiconductor quantum wire is investigated. We take into account the presence of an axial magnetic field along the direction of current flow and spin orbit interaction in the wire. If the wire contains a non-magnetic charged impurity, then the zero temperature interface conductance depends strongly on the exact location of this impurity. When calculated as a function of the applied gate bias, the spin injection efficiency is a much more sensitive function of the location and strength of the scattering potential for an attractive scatterer. However, at absolute zero temperature, an injection efficiency close to 100% can be obtained for both types of impurities if carriers are injected with energies that coincide with the Zeeman energy states in the wire. The temperature dependence of maximum spin injection efficiency is calculated for both attractive and repulsive impurity potentials.