Epitaxy and Electronic Properties of Ultrawide Bandgap Aluminum Oxynitride Films

Aluminum oxynitride with an ultrawide bandgap is a promising material for electronic devices due to its high dielectric constants and low leakage currents. A comprehensive understanding of the electronic properties of single-crystalline or epitaxial aluminum oxynitride films is crucial for the design of high-performance electronic devices. However, research on this topic remains limited due to the lack of epitaxial aluminum oxynitride films. In this study, we report on the electronic properties of epitaxial aluminum oxynitride films synthesized by magnetron sputtering. The crystal structures of the aluminum oxynitride films were characterized by high-resolution X-ray diffraction, while their electronic properties were investigated through X-ray photoelectron spectroscopy and optical absorption spectroscopy, revealing an ultrawide bandgap of 5.23 eV. Additionally, the bandgap between the Fermi level and the valence band maximum is measured at 3.6 eV. Interestingly, the measurements of the leak current density demonstrate that the breakdown field (9.1 MV/cm) of epitaxial aluminum oxynitride thin films (∼12 nm) in this work is significantly higher than that (4–6 MV/cm) of most amorphous aluminum oxynitride films. Our results provide a way for synthesizing high-quality epitaxial aluminum oxynitride films and uncover their physical properties, which are fundamental for designing high-performance electronic devices such as highly reliable ferroelectric field-effect transistor (FeFET) memory devices.