Abstract: A method is disclosed for depositing a high-quality thin films of ultrawide bandgap oxide semiconductors at growth rates that are higher than possible using prior-art methods. Embodiments of the present invention employ LPCVD deposition using vapor formed by evaporating material as a precursor, where the material has a low vapor pressure at the growth temperature for the thin film. The vapor is carried to a reaction chamber by an inert gas, such as argon, where it mixes with a second precursor. The reaction chamber is held at a pressure that nucleation of the precursor materials occurs preferentially on the substrate surface rather than in vapor phase. The low vapor pressure of the material gives rise to growth rates on the substrate surface that a significantly faster than achievable using prior-art growth methods.