Pulsed-Liquid-Injection MOCVD of Epitaxial β‑Ga₂O₃ Thin Films as a Promising Alternative Chemical Route

The development of β-Ga₂O₃ thin films has received over the past years an increasing interest for power electronics devices. Here, we investigate the relatively unexplored growth of β-Ga₂O₃ thin films on a c-plane sapphire substrate using pulsed-liquid injection metal-organic chemical vapor deposition (PLI-MOCVD). In contrast to conventional MOCVD, the atomization and flash vaporization processes allow for a more precise dosing of the chemical precursors kept at room temperature for the sake of sustainability and gallium criticality. By using triethyl gallium and O₂ molecules, we show the PLI-MOCVD of epitaxial β-Ga₂O₃ thin films with a growth rate of around 148 ± 5 nm/h and a RMS surface roughness of 1.5 ± 0.1 nm. The single-crystalline nature of the β-Ga₂O₃ thin films, composed of multiple rotational domains, reveals the following epitaxial relationships: β-Ga₂O₃ (-201) || α-Al₂O₃ (003) and β-Ga₂O₃ (020) || α-Al₂O₃ (300). The β-Ga₂O₃ thin films are fully stoichiometric with an optical bandgap energy of 4.8 ± 0.2 eV. The presence of carbon, likely substituting, to some extent, for oxygen sites, eventually explains some of the yellow-to-UV emission bands using optical spectroscopy. These findings demonstrate that PLI-MOCVD in a vertical cold-wall configuration represents a promising alternative, reproducible chemical route to obtain epitaxial β-Ga₂O₃ thin films with high quality, while being well aligned with the efficiency- and safety-related principles of green chemistry.