Effect of Sc concentration on shear wave velocities in ScAlN films measured by micro-Brillouin scattering technique

ScAlN film is attractive for the BAW and SAW resonators because of its large piezoelectric constants compared with AlN and ZnO. However, the shear and longitudinal elastic properties perpendicular to the c-axis, which are required for SAW and BAW analyses, have not been reported. In this study, we measured shear and longitudinal wave velocities propagating perpendicular to the c-axis [v_S = (c₆₆/ρ)^1/2 and v_L = (c₁₁/ρ)^1/2] in ScAlN films with various Sc concentrations using micro-Brillouin scattering technique. The shear and longitudinal wave velocities in the Sc_0.41Al_0.59N films decreased to 69% and 81% of those in a pure AlN film, respectively. The shear wave velocity in the film with Sc concentration more than 50% increased with increasing of Sc concentration.