Local structure around Fe in the diluted magnetic semiconductors Ga_1−xFe_xAs studied by x-ray absorption fine structure

Extended x-ray absorption fine structure and near-edge x-ray absorption fine structure techniques are employed to investigate the local structure and valency about Fe atoms in the diluted magnetic alloy semiconductor system Ga_1−xFe_xAs prepared by molecular-beam epitaxy under various conditions. This experiment is aimed at elucidating possible correlations between the microstructures in these diluted magnetic semiconductors and some physical properties. Our x-ray results offer direct evidence of Fe substitution for Ga sites in GaAs prepared at relatively low substrate temperatures, wherein the Ga_1−xFe_xAs compound is mainly paramagnetic. However, the Fe impurity atoms could form small Fe clusters and/or Fe-As complexes when the samples are grown at high temperatures.