Polarization-dependent XAFS and density functional theory investigations of the quality of the epitaxial GaMnN structure

Ferromagnetic GaMnN in which manganese substitutes randomly gallium, can constitute a major technological advance, especially due to the already dominating role of group III nitrides in photonics and high power electronics. However, obtained till now results concerning the nature of magnetism of (Ga,Mn)N, can be often related to defects as the main factors determining the properties of the material. Non-polarization and polarization-dependent EXAFS analysis have been used in order to investigate the local structure of homogenous GaMnN. The analysis points on nitrogen defects such as vacancies (VN) as well as on additional N atoms in the first coordination shell in the GaMnN structure. Moreover, the presence of oxygen atoms in bulk samples with 5 and 7% Mn was confirmed. Inclusions of metallic Mn and oxygen atoms on the Ga0.9Mn0.1N surface were detected. The theoretical reconstruction of the XANES spectra using density functional theory (DFT) affirms the presence of the nitrogen defects.