Structural characterization of epitaxial ScAlN films grown on GaN by low-temperature sputtering

ScAlN has garnered substantial attention for its robust piezoelectric and ferroelectric properties, holding promise for diverse electronic device applications. However, the interplay between its structural attributes and physical properties remains poorly understood. This study systematically elucidates the structural characteristics of epitaxial ScAlN films grown on GaN by low-temperature sputtering. Correlations between Sc composition, lattice constants, and film strains were revealed utilizing high-resolution X-ray diffraction, reciprocal space mapping, and machine learning analyses. Our machine-learning model predicted c-axis lattice constants of ScAlN grown on GaN under various conditions and suggested that sputtering permits coherent growth over a wide compositional range. These findings advance the understanding of ScAlN and provide valuable insights for the research and development of novel ScAlN-based devices.