β-Al2xGa2-2xO3 Thin Film Growth by Molecular Beam Epitaxy

β-Al 2 x Ga 2-2 x O 3 alloy thin films were successfully grown on (100)-oriented β-Ga 2 O 3 single-crystal substrates by plasma-assisted molecular beam epitaxy. The films were grown almost coherently and maintained the β-phase up to an Al content of x =0.61. Below an Al content of about x =0.4, step-flow growth was achieved, and carrier accumulation was observed at the heterointerface. These results encourage further research into β-Al 2 x Ga 2-2 x O 3 thin films and associated devices, especially high-electron-mobility transistors for high-power applications.