Impact of an annealing atmosphere on band-alignment of a plasma-enhanced atomic layer deposition-grown Ga2O3/SiC heterojunction

Abstract

Gallium oxide (Ga₂O₃) has attracted much attention because of its notable advantages, including its low cost and a high critical breakdown field. In this study, atomic layer deposition was used to deposit high-quality Ga₂O₃ onto a SiC substrate with high thermal conductivity. The band arrangement of the Ga₂O₃/SiC heterojunction was investigated by modulating oxygen vacancies using different post-annealing atmospheres. The results demonstrated that recrystallization of Ga₂O₃ resulted in a good crystalline state because of the rearrangement of Ga and O atoms following high-temperature annealing. Simultaneously, the roughness of all annealed samples increased. X-ray photoelectron spectroscopy analysis revealed a significant reduction of oxygen vacancy content in samples that were annealed in an oxygen atmosphere; this is attributed to the replacement of oxygen vacancies by oxygen atoms. Conversely, oxygen vacancies increased in an oxygen-free environment. The band offsets (valence band, conduction band) were respectively determined to be (−1.03 eV, 0.5 eV), (−0.63 eV, 0.9 eV), (−1.39 eV, 0.16 eV), and (−1.32 eV, 0.22 eV) for the as-deposited sample and annealed samples with O₂, N₂, and Ar atmospheres. Finally, the impact that various ratios of oxygen vacancies have on the energy band structure of Ga₂O₃ was studied using first-principles calculations. Calculations on heterojunctions confirmed that the introduction of oxygen vacancies reduced the potential barrier at the interface and promoted the movement of electrons. Thus, this study provides valuable insights for the design and application of Ga₂O₃/SiC heterojunction devices.