Atomic-Scale Strain Relaxation via Ar-Bombarded Surface Modification for Enabling Single-Crystalline β-Ga2O3 (010) Heteroepitaxy.

Gallium oxide (Ga2O3) is an emerging ultrawide bandgap semiconductor for high-power electronics and solar-blind optoelectronics. Here we demonstrate an atomic-scale strain relaxation method to achieve a complete α-to-β Ga2O3 phase transition within the initial nucleation stage, enabling a heteroepitaxial growth regime of single-crystalline β-Ga2O3 (010) films. An Ar+ bombardment strategy is used to create periodic strain relaxation sites that relieve the compressive strain in the metastable α-Ga2O3 interlayer and facilitate the phase transition, as revealed by a combination of X-ray diffraction, atomic-force microscopy, atomic-resolution scanning transmission electron microscopy, and geometric phase analysis. The heteroepitaxial Sn-doped β-Ga2O3 (010) films with distinct donor activation behavior are established on m-plane sapphire, and a lateral Schottky barrier diode with a high reverse breakdown voltage of 1590 V is achieved. This study provides critical insights into atom-scale strain engineering and confined epitaxial growth for developing high-quality β-Ga2O3 films on cost-effective substrates for advanced electronic devices.