Analysis of Sezawa mode Rayleigh-type SAWs on ScAlN film/floated electrode layer/ScAlN film/high velocity substrates

Abstract

Surface acoustic wave (SAW) devices for frequency filters are increasingly required to have high performance in future mobile communications. The coupling factors K 2 for Rayleigh-type SAW (RSAW) on ScAlN film/high velocity substrate structures can be enhanced by introducing polarization-reversal structure into the ScAlN film. However, the growth of polarization-reversal ScAlN films with high crystal orientation would be very difficult. In this study, the Sezawa mode RSAWs on layered structures consisting of ScAlN films with floated intermediate electrode layer/high velocity substrates were analyzed by using Farnell and Adler’s SAW propagation analysis and finite element method. We found that the K 2 values of the Sezawa modes were enhanced by inserting the floated intermediate electrode layer without using polarization reversal structure, which were higher than those of the polarization-reversal ScAlN films/high velocity substrates. The enhancement of K 2 would be due to the improvement of the SAW energy concentration at the ScAlN film surface.