Fabrication of tunable bandgap epitaxial β ‐(Al _x Ga _{1− x} ) ₂ O ₃ films using a spin‐coating method

Abstract β ‐(Al _x Ga _{1− x} ) ₂ O ₃ films have several critical properties of interest to the research community, including a wide bandgap that may be used in the development of new electronic, optoelectronic, and photonic devices. Here we demonstrate the first time fabricated metal‐alkoxide‐based spin‐coated single‐phase epitaxial β ‐(Al _x Ga _{1− x} ) ₂ O ₃ films on c ‐sapphire substrates with orientation and good crystallinity that is comparable to the films fabricated using other film deposition techniques, such as molecular beam epitaxy and chemical vapor deposition. Using this technique, we generated films with broad Al compositions ( x ) of 0.3, 0.5, and 0.7 with bandgap energies of 5.15, 5.56, and 6.16 eV, respectively, estimated from the X‐ray photoelectron spectroscopy inelastic energy‐loss spectra. Photoluminescence emission spectra in the ultraviolet and visible (blue) wavelength range highlighted several intrinsic defects in the film structure that functioned as luminescence centers, including self‐trapped exciton and recombining donor‐to‐acceptor band. Detailed analysis of the structural and optical properties of β ‐(Al _x Ga _{1− x} ) ₂ O ₃ epitaxial films revealed that this low‐cost and scalable solution‐deposition approach coupled with a spin‐coating technique could be used to fabricate β ‐(Al _x Ga _{1− x} ) ₂ O ₃ films with tunable properties.