In situ observation of secondary phase formation in Fe implanted GaN annealed in low pressure N2 atmosphere

The formation of secondary phases in Fe implanted GaN upon annealing in low pressure N2-atmosphere was detected by means of in situ x-ray diffraction and confirmed by magnetization measurements. A repeatable phase change from Fe3N at room temperature and Fe3−xN at 1023 K was observed in situ. The phase transformation is explained by the change of lattice site and concentration of nitrogen within nitrides. The diffusion of Fe toward sample surface and oxidation with increasing annealing cycles limits the availability of secondary phase and hence the repeatability. At high temperature GaN dissolves and Ga as well as Fe oxidize due to presence of residual oxygen in the process gas. The ferromagnetism in the samples is related to nanometer sized interacting Fe3−xN crystallites.