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 (Ga 2 O 3 ) thin films. Ga 2 O 3 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 Ga 2 O 3 thin films was thoroughly investigated. All annealed films exhibited a polycrystalline β-Ga 2 O 3 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 Ga 2 O 3 /SiO 2 heterostructure formation, with Ga 2 O 3 thickness decreasing and SiO 2 thickness increasing with longer annealing times. These findings enhance the understanding of the role of annealing in optimizing Ga 2 O 3 thin films for electronic and optoelectronic applications. • As-Deposited Ga 2 O 3 film is amorphous; all annealed films are partially crystalline. • Post-annealing at 1000 °C promotes the formation of Ga 2 O 3 /SiO 2 heterostructure. • Prolonged annealing creates oxygen vacancies within Ga 2 O 3 , lowering the bandgap.