The influence of the Fe/Ga0.9Al0.1As interface on spin injection into a spin light-emitting diode is studied. Spin injection is found to depend strongly on the interfacial doping profile demonstrating the importance of band bending in the semiconductor near the interface. The effect of post-growth annealing on spin injection from Fe contacts into GaAs-based spin light-emitting diodes is also examined. Post-growth annealing up to 250 degrees C is found to increase the spin injection efficiency. It is demonstrated that the annealing modifies electronic properties of the Fe/Ga0.9Al0.1As interface, as evidenced by an increase of the Schottky barrier height. (c) 2005 American Vacuum Society.