【Epitaxy Papers】Rotational domains and origin of improved crystal quality in heteroepitaxial（-201）β-Ga₂O₃ films grown on vicinal substrates by MOCVD

      Researchers from the Slovak Academy of Sciences have published a dissertation titled "Rotational domains and origin of improved crystal quality in heteroepitaxial（-201）β-Ga₂O₃ films grown on vicinal substrates by MOCVD" in Journal of Alloys and Compounds.

Abstract

      Monoclinic gallium oxide (β-Ga₂O₃) is a promising material for high-power and high-voltage electronic devices. Homoepitaxial β-Ga₂O₃ films offer superior crystalline quality but face limitations in scalability, substrate cost, and thermal management. Heteroepitaxy on substrates such as sapphire, SiC, and Si provides a practical alternative, yet often yields high defect densities and degraded film properties. Substrates with hexagonal surface symmetry in particular promote in-plane rotational domains (IRDs), further compromising film quality. To investigate the relationship between IRDs and substrates with partially broken hexagonal surface symmetry, (-201) β-Ga₂O₃ films were grown on vicinal c-plane sapphire with off-cut angles ranging from 0° to 10° toward the a-plane using liquid-injection metalorganic chemical vapor deposition. Contrary to previous reports, no significant IRD suppression was observed at any off-cut angle. Pole-figure measurements proved to be essential for detecting all IRDs, while conventional azimuthal X-ray diffraction (XRD) scans could provide spurious results. Despite the presence of six IRDs, off-cut substrates improved crystal quality, surface roughness, and electrical performance of (-201) β-Ga₂O₃ films. Analysis revealed reduced mosaicity perpendicular to substrate surface steps as evidenced by decrease of the XRD rocking curve full-width-at-half-maximum from ~2.1° down to ~1.1° for sapphire off-cut angles of 0° and 10°, respectively. Also observed was an effective suppression of (310)-oriented β-Ga₂O₃ crystals; ~100 times lower (310)/(-201) XRD intensity ratio was found for the sapphire with 10° off-cut angle. These findings clarify the nuanced role of vicinal substrates, showing that IRD suppression may resist conventional approach of breaking the surface symmetry by employing the vicinal substrates.

DOI：

https://doi.org/10.1016/j.jallcom.2025.184481