Au-Nanoparticle-Assisted Pulsed-Laser Deposition of Ga ₂ (O _{1– <i>x</i>} S <i> _x </i> ) ₃ Epitaxial Films

We report the impact of Au nanoparticles on the efficiency of S incorporation into β-Ga2O3 films grown on (100) MgO substrates by pulsed-laser deposition (PLD) with GaS as a solid source. Prior to PLD, thin Au layers were vacuum-deposited and dewetted. The dewetted Au layers were transformed into fine nanoparticles, which significantly facilitated not only the sulfurization of Ga but also the growth rate at growth temperatures (Tg) higher than 600 °C. As a result, (100)-oriented Ga2(O1–xSx)3 films with x as high as 0.38 were obtained. Despite notable compositional fluctuations, the band gap energy was tuned from 3.7 to 4.4 eV by changing Tg and Au-layer thickness. Moreover, we revealed that the amount of effective Au nanoparticles, measured from the dependence of S content in the films on equivalent Au-layer thickness, was in a range from 0.4 to 1.5 nm. These results indicate that Au-nanoparticle-assisted PLD is a useful method for the band gap engineering of β-Ga2O3 through anion substitution with S.