Epitaxial growth of α-(AlxGa1− x) 2O3 by suboxide molecular-beam epitaxy at 1 µm/h

摘要: We report the use of suboxide molecular-beam epitaxy (S-MBE) to grow α-(AlxGa1− x) 2O3 films on (110) sapphire substrates over the 0< x< 0.95 range of aluminum content. In S-MBE, 99.98% of the gallium-containing molecular beam arrives at the substrate in a preoxidized form as gallium suboxide (Ga2O). This bypasses the rate-limiting step of conventional MBE for the growth of gallium oxide (Ga2O3) from a gallium molecular beam and allows us to grow fully epitaxial α-(AlxGa1− x) 2O3 films at growth rates exceeding 1 μm/h and relatively low substrate temperature (Tsub= 605±15○ C). The ability to grow α-(AlxGa1− x) 2O3 over the nominally full composition range is confirmed by Vegard’s law applied to the x-ray diffraction data and by optical bandgap measurements with ultraviolet–visible spectroscopy. We show that S-MBE allows straightforward composition control and bandgap selection for α-(AlxGa1− x …