Electron spin resonance in GaN thin film doped with Fe

High-quality and high-resistivity semiconducting substrates are needed to fabricate high-frequency devices Such as high-mobility transistors based on gallium nitride (GaN). A GaN thin film doped with Fe ions becomes one of Such high-resistivity Substrates. To obtain microscopic information on the Fe ions in the GaN:Fe film, we have performed electron spin resonance (ESR) measurements using a conventional X-band apparatus and home made Q-band equipment. The observed ESR signals were analyzed with a spin Hamiltonian given by considering the local symmetry of the Ga site (C-3r) and assuming that the Fe3+ ions (S = 5/2) are substituted for Ga3+ ions. As a result, the angular dependence of the resonance fields and the temperature dependence of the signal intensities are reproduced Very Well by the calculations. Consequently, we confirmed that the Fe3+ ions occupy some of the Ga sites in the GaN thin film.