Substrate orientation-dependent domain formation in epitaxial NiO/β-Ga2O3 heterostructures via Mist-CVD

The interfacial configuration in oxide heteroepitaxy plays a critical role in determining the structural integrity and reliable performance of wide-bandgap heterostructures. Herein, we investigate the orientation-dependent epitaxial growth of high-quality NiO films on β-Ga 2 O 3 via mist chemical vapor deposition (Mist-CVD), exhibiting distinct epitaxial domain configurations depending on the substrate orientation. Combined experimental and density functional theory (DFT) analyses reveal that the synergistic interplay among surface energy, lattice mismatch, and crystal symmetry governs the epitaxial mode and crystalline quality across different substrate orientations. Benefiting from the high-quality epitaxy, the NiO films demonstrate good environmental stability, retaining 94% of their initial current after 30 days of ambient exposure. As a functional demonstration, the NiO/(001) β-Ga 2 O 3 p-n diode exhibits a low leakage current density (2.08 ×10 −8 A·cm −2 @-100 V) and a high breakdown voltage of 885 V, highlighting the critical role of epitaxial interface quality. This study provides mechanistic insight into orientation-regulated oxide heteroepitaxy and offers a viable materials strategy for constructing stable wide-bandgap oxide heterostructures.