Rayleigh waves in nonpolar Al_0.7Sc_0.3N(11 2¯0) films with enhanced electromechanical coupling and quality factor

This work reports on the growth of 1 µm nonpolar a-plane Al0.7Sc0.3N(11[Formula: see text]0) thin films on an r-plane sapphire Al2O3(1[Formula: see text]02) via magnetron sputter epitaxy. The electro-acoustic properties of the film structures were characterized using surface acoustic wave (SAW) resonators. Measured electrical responses were found to be strongly anisotropic in terms of the wave propagation direction. We identified a sagittal polarized Rayleigh wave mode with large coupling ([Formula: see text] 3.7%), increased phase velocity ([Formula: see text] 4825 m/s), as well as high quality factor ( Q > 1000) for SAW propagation along the c-axis [0001] and normalized thicknesses [Formula: see text]. Finite element method simulations using electro-acoustic properties of Al0.7Sc0.3N obtained from the density functional theory reproduce our experimental results.