Magneto-optical properties of group-IV ferromagnetic semiconductor Ge_(1-x)Fe_x grown by low-temperature molecular beam epitaxy

摘要

Group-IV ferromagnetic semiconductor Ge_(1-x)Fe_x was grown by low-temperature molecular beam epitaxy without precipitation of ferromagnetic Ge-Fe intermetallic compounds. The ferromagnetism of Ge_(1-x)Fe_x films was investigated by magnetic circular dichroism (MCD). In particular, the influence of the Fe content (X=2.0 PERCENT-17.5 PERCENT) and growth temperature (100 and 200 deg C) on the ferromagnetism was carefully studied. The MCD measurements revealed that the overall spectral features reflecting the band structure of the Ge_(1-x)Fe_x films were identical with those in bulk Ge, and that the large spin splitting of the band structure was induced by the incorporation of Fe atoms into the Ge matrix, indicating the existence of s,p-d exchange interactions. The Ge_(1-x)Fe_x films showed ferromagnetic behavior and the ferromagnetic transition temperature linearly increased with increasing the Fe concentration. These results indicate that the epitaxially grown Ge_(1-x)Fe_x is an intrinsic ferromagnetic semiconductor.