Tailoring oxygen vacancies in Ga₂O₃ thin films and controlled formation of Ga₂O₃/SiO₂ heterostructures via annealing

This study examines the effects of annealing duration on the oxygen vacancies in gallium oxide (Ga₂O₃) thin films. Ga₂O₃ thin films were deposited by RF magnetron sputtering on (100) silicon substrates and subsequently annealed in an argon atmosphere at 1000 °C for 1, 2, 4, and 7 h. The impact of the annealing time on the morphology, oxygen content, optical bandgap, and thickness of Ga₂O₃ thin films was thoroughly investigated. All annealed films exhibited a polycrystalline β-Ga₂O₃ phase with a monoclinic crystal structure and a preferred orientation along the (400) plane. Increasing the annealing time resulted in larger grains, a denser interfacial layer, and reduced microstrain. Prolonged annealing also facilitated the escape of oxygen atoms, creating oxygen vacancies that formed a defect band below the conduction band, significantly lowering the optical bandgap. Cross-sectional transmission electron microscopy revealed a Ga₂O₃/SiO₂ heterostructure formation, with Ga₂O₃ thickness decreasing and SiO₂ thickness increasing with longer annealing times. These findings enhance the understanding of the role of annealing in optimizing Ga₂O₃ thin films for electronic and optoelectronic applications.