Pre-edge features in X-ray absorption structure of Mn in GaMnN, GaMnAs and GeMn

Ga1-xMnxNGa1-xMnxN samples with a wide range of concentrations, from x=0.003x=0.003 to 0.057, were grown by molecular beam epitaxy. X-ray diffraction and the simulation of the extended X-ray absorption fine structure (EXAFS) confirmed the wurtzite structure of the samples, without any secondary phase, and the location of Mn in the gallium sublattice of GaN. The valence state of Mn was studied using the X-ray absorption near-edge structure (XANES) at the K-edge of Mn. The shape of the measured XANES spectra does not depend on the Mn concentration: that implies the same valence state and local atomic structure around the Mn atom in all samples. A calculation of the electronic band structure of GaMnN, GaMnAs, GeMn and the XANES spectra of Mn in GaMnN was performed using the linearized augmented plane wave (LAPW) method. The calculated spectra fit well our experimental data. In particular, the comparison demonstrates that a peak in the pre-edge structure is directly related to the 3+3+ valence state of Mn. This was confirmed experimentally by measurements of the Mn K-edge in GaMn2+AsGaMn2+As and ZnMn2+TeZnMn2+Te. An application of proposed interpretation for GeMn is discussed.