Nucleation-Accelerated Epitaxy at Large-Area (100) β‑Ga₂O₃ Terraces

Even though epitaxy is synonymous with order, its practical realization often depends on the availability of surface sites that locally break ideal flatness, such as steps and kinks, where adatoms can be efficiently incorporated. This challenge is well-known for homoepitaxial growth of thermodynamically stable monoclinic gallium oxide (β-Ga₂O₃) on (100) substrates, which in the as-cleaved exhibit large-area, atomically flat terraces with a low density of step edges. To address this problem, we propose a self-organized process triggered by annealing that subdivides large-area terraces into narrower domains, with substeps corresponding to approximately half the unit cell height. Using such substep-templated substrates, we achieved a high growth rate of ∼2.83 μm h^-1, exceeding values reported for (100) β-Ga₂O₃ homoepitaxy in the literature, while maintaining reasonable structural quality and electronic functionality. By placing this substep-templating approach in the context of other nucleation-enhancing strategies for β-Ga₂O₃ homoepitaxy, we conclude that it provides a viable route to mitigate limitations associated with higher surface-energy planes or off-axis miscuts. Altogether, these results demonstrate a practical strategy for improving β-Ga₂O₃ homoepitaxy for advanced device applications.