Tailoring oxygen vacancies in Ga2O3 thin films and controlled formation of Ga2O3/SiO2 heterostructures via annealing
Asma O. Al Ghaithi, Inas Taha, Sumayya M. Ansari, Nitul S. Rajput, Baker Mohammad, Haila M. Aldosari
Abstract
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.