2026/05/22 by Arun Kumar Dhasiyan, Naohiro Shimizu, Osamu Oda +1
Materials Science · Physics and Astronomy · Energy · #Ga2O3 and related materials #GaN-based semiconductor devices and materials #Advanced Photocatalysis Techniques
paper · doi:10.1016/j.jcrysgro.2026.128681
Because of its ultra-wide bandgap of ∼4.85 eV and theoretically predicted critical field of up to 8 MV/cm 2 , β-Ga 2 O 3 is considered to be a potential candidate for next-generation power electronics. High-quality homoepitaxially grown β-Ga 2 O 3 thin films with a reasonably high growth rate and very smooth surface are essential for device applications. Although hydride vapor phase epitaxy offers exceptionally high growth rates suitable for thick drift layers, it suffers from a poor surface morphology, thickness nonuniformity, and chlorine contamination. Molecular beam epitaxy (MBE), which can produce high-quality films, is constrained by low growth rates owing to the volatility of gallium suboxide (Ga 2 O). To address these challenges, we developed a high-density oxygen radical source (HD-ORS) that leverages the ozone-induced generation of oxygen atoms. This reactive species efficiently oxidizes transient Ga 2 O into stable Ga 2 O 3 , thereby suppressing Ga desorption and enhancing precursor utilization. HD-ORS enables β-Ga 2 O 3 growth at temperatures as low as 300 °C with rates of 1 µm/h by MBE. Despite these advantages, the resulting films include grains with the β-Ga 2 O 3 (40–1) orientation, together with those having the β-Ga 2 O 3 (100) orientation. Physical vapor deposition (PVD) was used to make a systematic comparison between the HD-ORS and a conventional low-impedance antenna inductively coupled plasma source, which showed that the HD-ORS delivered growth rates that were twice those available with the conventional source across a temperature range of up to 850 °C. At higher temperatures, this advantage became even more pronounced, and the resulting Ga 2 O 3 films exhibited (001)-oriented epitaxial growth, highlighting the superior reactivity of oxygen atoms in maintaining a high incorporation efficiency. These findings established the HD-ORS as a transformative oxygen source for MBE and PVD, enabling rapid, controlled, and scalable β-Ga 2 O 3 epitaxy. Beyond improving the growth kinetics, mechanistic insights highlighted the pivotal role of reactive oxygen species in oxide semiconductor fabrication, offering a pathway toward high-performance, reliable, and vertical power devices.