Influence of oxygen annealing conditions on the electronic structure, dielectric function, and charge conduction of gallium-ferrite thin films

Gallium-ferrite thin films were studied to investigate the effects of the oxygen annealing conditions on the electrical properties. Ga_0.8Fe_1.2O_3-δ thin films were prepared by using a sol-gel method under different oxygen partial pressures. The structural properties of the films were studied by using X-ray diffraction. X-ray photoemission spectra of the core-levels of Ga, Fe, and O in the films were examined. The dielectric functions of the films were measured at energies from 0.73 to 6.45 eV by using spectroscopic ellipsometry. The Fe valence was changed by the oxygen vacancies, which are dominantly responsible for the dielectric function and the charge conduction. Remarkably, the leakage current of the films annealed under intermediate oxygen atmospheric conditions showed the lowest values. In the film, the oxygen vacancies, were indirectly estimated by using the ratio of Fe²⁺ to Fe³⁺, are important to reduce the leakage current, which can be explained by using a space-charge-limited model with shallow traps.