This paper presents the homoepitaxy of Si-doped β-Ga₂O₃ thin films on semi-insulating (010) and (001) Ga₂O₃ substrates via low pressure chemical vapor deposition with a growth rate of ≥1 μm/h. Both high resolution scanning transmission electron microscopy and X-ray diffraction measurements demonstrated high crystalline quality homoepitaxial growth of these thin films. Atomic resolution STEM images of the as-grown β-Ga₂O₃ thin films on (010) and (001) substrates show high quality material without extended defects or dislocations. The charge carrier transport properties of the as-grown Si-doped β-Ga₂O₃ thin films were characterized by the temperature dependent Hall measurement using van der Pauw patterns. The room temperature carrier concentrations achieved for the (010) and (001) homoepitaxial thin films were ∼1.2 × 10¹⁸ cm⁻³ and ∼9.5 × 10¹⁷ cm⁻³ with mobilities of ∼72 cm²/V s and ∼42 cm²/V s, respectively.

This paper investigated the growth of (Al_xGa_1−x)₂O₃ thin films on semi-insulating (010) Ga₂O₃ substrates over the entire Al composition range (0% < x ≤ 100%) via metalorganic chemical vapor deposition (MOCVD). For the Al composition x < 27%, high quality single phase β-(Al_xGa_1−x)₂O₃ was achieved. A mixture of β and γ phases existed in (Al_xGa_1−x)₂O₃ when Al composition ranged between 27% and 40%, whereas a single γ-phase was observed for the films with Al composition x > 40%. The transition from the β to γ phase in AlGaO alloys was observed from x-ray diffraction spectra. The growth of γ-phase AlGaO with higher Al content was further confirmed via atomic resolution scanning transmission electron microscopy imaging and nanodiffraction. Compositional and statistical analyses performed on data acquired from atom probe tomography provided insight on the local compositional homogeneity in AlGaO films with different Al compositions. For AlGaO with pure β or γ phases, the Al composition distribution showed homogeneity with similar Al composition values as extracted from the x-ray diffraction peak positions. For AlGaO films with mixed β and γ phases, inhomogeneity in the Al composition distribution became more obvious in the nm scale. A mechanism was proposed for the observed phase transformation between β and γ phases in MOCVD growth of AlGaO films.