Single-Crystalline β-GaO Homoepitaxy on a Near Van der Waals Surface of (100) Substrate.

Gallium oxide (Ga₂O₃) is a promising wide-bandgap semiconductor for power devices, offering high breakdown voltage and low on-resistance. Among its polymorphs, β-Ga₂O₃ stands out due to the availability of high-quality, large-area single-crystalline substrates, particularly on the (100) surface, grown via melt-based bulk crystal growth. However, the low surface energy of β-Ga₂O₃ (100), akin to 2D materials, presents challenges in homoepitaxy, including poor nucleation and twin formation, which hinder its practical application. This study demonstrates the successful homoepitaxial growth of single-crystalline β-Ga₂O₃ on (100) substrates using a van der Waals epitaxial approach. By introducing an excess surfactant metal in metal-rich conditions at high temperature, a growth regime approximate thermal equilibrium is achieved, enhancing adatom diffusion and suppressing metastable twin phases. This adjustment enables the formation of well-ordered, single-crystalline nuclei and lateral stitching in a half-layer-by-half-layer growth mode, similar to 2D material growth. The result is twin-free, atomically flat, single-crystal thin films on on-axis β-Ga₂O₃ (100) substrates. These findings significantly improve the crystalline quality of epitaxial β-Ga₂O₃ on (100) substrates, demonstrating their potential for scalable production of high-performance, cost-effective β-Ga₂O₃-based power devices, and advancing their feasibility for industrial applications.