In Situ Dielectric Al₂O₃/β-Ga₂O₃ Interfaces Grown Using Metal–Organic Chemical Vapor Deposition

High quality dielectric-semiconductor interfaces are critical for reliable high-performance transistors. This paper reports the in situ metal–organic chemical vapor deposition of Al₂O₃ on β-Ga₂O₃ as a potentially better alternative to the most commonly used atomic layer deposition (ALD). The growth of Al₂O₃ is performed in the same reactor as Ga₂O₃ using trimethylaluminum and O₂ as precursors without breaking the vacuum at a growth temperature of 600 °C. The fast and slow near interface traps at the Al₂O₃/β-Ga₂O₃ interface are identified and quantified using stressed capacitance–voltage (CV) measurements on metal oxide semiconductor capacitor (MOSCAP) structures. The density of shallow and deep level initially filled traps (D_it) are measured using ultraviolet-assisted CV technique. The average D_it for the MOSCAP is determined to be 6.4 × 10¹¹ cm⁻²eV⁻¹. The conduction band offset of the Al₂O₃/ Ga₂O₃ interface is also determined from CV measurements and found out to be 1.7 eV which is in close agreement with the existing literature reports of ALD Al₂O₃/Ga₂O₃ interface. The current–voltage characteristics are also analyzed and the average breakdown field is extracted to be approximately 5.8 MV cm⁻¹. This in situ Al₂O₃ dielectric on β-Ga₂O₃ with improved dielectric properties can enable Ga₂O₃-based high-performance devices.