Characteristics of molecular beam epitaxy-grown GaFeAs

Diluted magnetic semiconductors GaFeAs were grown by molecular beam epitaxy and characterized. Ga_1-xFe_xAs ternary alloys were obtained at the growth temperature T_s = 200 °C ranging from x = 0:005 to 0.03. The effects of thermal treatment on behaviors of defects, affecting to the magnetic properties of GaFeAs layer were particularly elucidated. As-grown samples were annealed at temperatures varying from 400 to 600 °C. From the measurement of double crystal X-ray diffraction, we observed Fe-related peak which shifted to a higher diffraction angle as the Fe content increased, indicating that the lattice constant decreases with increasing Fe content. In contrast, above the annealing temperature 500 °C, the lattice constant becomes smaller than that of GaAs. Using the deep level transient spectroscopy, various defects in GaFeAs layer were observed and identified in conjunction with magnetic properties.