Dispersion of Refractive Index of β-Ga2O3 Thin Films

The dispersion of the refractive index of β-Ga2O3 thin films obtained by RF-sputtering was investigated. Anomalous dispersion was observed for films annealed in hydrogen; normal dispersion, for films annealed in oxygen or argon. The spectral dependence in the visible region of the refractive index with normal dispersion was determined mainly by transitions from the top of the valence band formed by oxygen 2p-states to the bottom of the conduction band formed by hybridization of oxygen 2p-states and gallium 4s-states. The single-oscillator approximation parameters, dispersion energy, degree of ionic chemical bonding, and coordination number were found for films with normal dispersion.