Propagation characteristics of longitudinal-type leaky surface acoustic wave on layered structure consisting of Sc<i>_x</i>Al₁₋<i>_x</i>N film/LiNbO₃substrate

Abstract

A longitudinal-type leaky surface acoustic wave (LLSAW) has a high phase velocity. Therefore, LLSAW devices are suitable for applications to high-frequency filters. However, the attenuation of LLSAWs is higher than that of other SAW modes. This higher attenuation of LLSAWs, which causes a low Q factor, can be reduced by growing a higher-velocity film on a piezoelectric substrate. On the other hand, K2 in the layered structure decreases because of the small piezoelectricity in high-velocity films. In this study, LLSAW propagation characteristics on a layered structure consisting of high-piezoelectric ScAlN film/X-cut 36°Y-propagation LiNbO3 were investigated. When a or ScAlN film was loaded, the reduction of the attenuation was observed, but K2 for this layered structure is lower than that of LiNbO3. On the other hand, K2 for Sc0.4Al0.6N film/LN is higher than that of LiNbO3.