Density of States and Interband Light Absorption in β-Ga2O3 Thin Films

The long-wavelength edge of the fundamental absorption band of beta-Ga2O3 thin films obtained by radio-frequency ion-plasma sputtering is studied. The edge of interband absorption during annealing of the films in oxygen, argon, and hydrogen is shown to be approximated well by the Urbach empirical rule. A model of a heavily doped or defective semiconductor in the quasi-classical approximation was used to analyze the experimental results. This model could be used to determine the radius of the basic electronic state a, the shielding radius r(S), and the rootmean-square potential Delta.