Highly coupled leaky surface acoustic wave on hetero acoustic layer structures based on ScAlN thin films with a c-axis tilt angle

Abstract

In this paper, hetero acoustic layer (HAL) structures based on ScAlN thin film with c-axis tilt angle are presented. The excitation SAW modes and their propagation characteristics for different Euler angles (0°, θ, ψ) of the ScAlN thin film were analyzed by finite element method. It is found that the acoustic field distribution for the HAL structures can be adjusted by rotating the Euler angle, and normal SAW are suppressed meanwhile leaky SAWs (LSAWs) with significantly improved electromechanical coupling coefficient (K2) are excited. The maximum K2 of 14% for SH-type LSAW can be obtained, which is almost 7 times larger than that of the previously reported normal SAW Sezawa mode. Moreover, the optimized HAL structure of (0°, 90°, 60°) ScAlN thin film/SiO2/AlN/Si possesses larger K2, wider bandwidth and higher Q value simultaneously, which is promising for the design and application of wideband SAW devices with high performance.