We discuss the effect of annealing on the interfacial structure of Fe/GaAs films, with 2 × 4 surface reconstructions, and the subsequent effect on the Schottky barrier height. Images of the interfaces indicate that the annealing process can greatly reduce the level of atomic mixing. A study of the I-V characteristics of Fe/GaAs Schottky barrier diodes, in a wide temperature range of 10-300 K, reveals a strong temperature dependence for the unannealed case, arising from the presence of mixed surface states. The annealing process reduces the existence of the interfacial states, leading to more ideal behavior, with a reduced temperature dependence of the Schottky behavior.