Conductance anisotropy of MOCVD-grown α-Ga2O3 films caused by (010) β-Ga2O3 filament-shaped inclusions

Abstract A significant anisotropy in the electrical conductance was observed in Si-doped α -Ga 2 O 3 /sapphire samples grown via liquid-injection metal organic chemical vapor deposition. Additionally to epitaxial α -Ga 2 O 3 diffraction, x-ray diffraction (XRD) revealed maxima related to (010) β -Ga 2 O 3 . Transmission electron microscopy, atomic force microscopy (AFM), and Raman spectroscopy of undoped samples with similar XRD pattern confirmed the formation of (010) β -Ga 2 O 3 filaments in the epitaxial α -Ga 2 O 3 film. In Si-doped samples, conductive AFM and temperature-dependent current–voltage measurement on transmission line measurement resistors confirmed, that β -Ga 2 O 3 filaments were responsible for significantly higher conductivity along the 2 1 ˉ 1 ˉ 0 α -Ga 2 O 3 direction compared to [0001] α -Ga 2 O 3 direction. Current–voltage measurements of transistor structures suggested semiconducting behavior of the β -Ga 2 O 3 filaments embedded in the highly resistive α -Ga 2 O 3 films.