Bias dependence of spin injection into GaAs from Fe, FeCo, and (Ga,Mn)As contacts

Spin injection from Fe(001) and (Ga,Mn)As(001) into n-GaAs(001) was investigated using a method which provides two-dimensional cross-sectional images of the spin polarization in GaAs. While the distribution of the spin polarization below the injecting contact is nearly uniform for (Ga,Mn)As, a strong confinement near the contact edge is observed for Fe and FeCo. The spin polarization in GaAs changes sign when the injected current is reversed. Multiple sign reversals as a function of bias voltage as reported previously for Fe injectors are not observed with (Ga,Mn)As and Fe contacts grown on clean n++−GaAs in agreement with earlier results for an epitaxial FeCo injector.