Abstract: Optimizing the orientation of β-Ga₂O₃ has emerged as an effective strategy to design high-performance β-Ga₂O₃ device, but the orientation growth mechanism and approach have not been revealed yet. Herein, by employing AlN buffer layer, the highly preferred orientation of β-Ga₂O₃ (100) film rather than (-201) film is realized on 4H-SiC substrate at low sputtering power and temperature. Because β-Ga₂O₃ (100) film exhibits a slower growth speed than (-201) film, the former possesses the higher dangling bond density and the lower nucleation energy, and a large conversion barrier exists between these two orientations. Moreover, the AlN buffer layer can suppress the surface oxidation of the 4H-SiC substrate and eliminate the strain of β-Ga₂O₃ (100) film, which further reduces the nucleation energy and enlarges the conversion barrier. Meanwhile, the AlN buffer layer can increase the oxygen vacancy formation energy and decrease the oxygen vacancy concentration of β-Ga₂O₃ (100) film. Consequently, the solar-blind photodetector based on the oriented film exhibits the outstanding detectivity of 1.22 × 10¹² Jones and photo-to-dark current ratio of 1.11 × 10⁵, which are the highest among the reported β-Ga₂O₃ solar-blind photodetector on the SiC substrate. Our results offer in-depth insights into the preferred orientation growth mechanism, and provide an effective way to design high-quality β-Ga₂O₃ (100) orientation film and high-performance solar-blind photodetector.

Key words: β-Ga₂ O₃ (100) film, Orientation growth, AlN buffer layer, Solar-blind photodetector, DFT calculation