Post-annealing-free heteroepitaxial growth of (2¯01)-oriented β-Ga2O3 thin films on c-plane sapphire by low-temperature laser-assisted RF sputtering

β-Ga 2 O 3 is a promising ultrawide-bandgap semiconductor for next-generation power electronics and deep-ultraviolet optoelectronics, but its epitaxial growth generally requires substrate temperatures above 600 ℃ or post-annealing. Here, we report post-annealing-free heteroepitaxial growth of ( 2 ¯ 01) -oriented β-Ga 2 O 3 thin films on c-plane sapphire using a 1064 nm ytterbium pulsed laser-assisted radio frequency magnetron sputtering process. Preferentially oriented β-Ga 2 O 3 films were formed at 100–400 ℃, and a well-defined ( 2 ¯ 01) -oriented heteroepitaxial film was obtained at 400 ℃. To the best of our knowledge, this is among the lowest substrate temperatures reported for sputtering-based β-Ga 2 O 3 heteroepitaxy without post-annealing. RF power control experiments confirmed that increasing RF power alone did not reproduce the orientation selective growth achieved under laser irradiation. X-ray diffraction (XRD), reciprocal space mapping, φ-scan, high-resolution transmission electron microscopy (HR-TEM), and selected-area electron diffraction (SAED) confirmed the epitaxial relationship of β-Ga 2 O 3 ( 2 ¯ 01) ||Al 2 O 3 (0001), with six in-plane rotational domains. The 400 ℃ film exhibited a sharp interface, a density of 6.34 g/cm 3 , and an optical bandgap of 4.95 eV. XPS showed enhanced Ga–O bonding and reduced oxygen-vacancy-related components at higher substrate temperatures. These results demonstrate laser-assisted RF sputtering as an effective low-thermal-budget route for β-Ga 2 O 3 heteroepitaxy on sapphire without post-annealing.