Dependence of the different elastic constants of ScAlN films on Sc content: A Brillouin scattering study with polarization analysis

The production and the characterization of high-quality ScAlN films, whose electromechanical coupling is larger than those of traditional AlN films, is attracting interest to develop the next generation of bulk acoustic wave resonators for mobile communications. We have exploited the Brillouin light scattering technique (BLS) to achieve a detailed elastic characterization of both AlN and ScAlN films with Sc concentration of 6% and 9.5%. By accurate control of the polarization state of both the incoming and the scattered light, we could detect and identify several distinct acoustic modes, achieving a determination of the whole set of five independent elastic constants and comparing them to recent theoretical predictions based on density functional theory.