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.
Enriquez et al. (Thu,) studied this question.