SAW Resonators on 15°YX-LiNbO3/SiO2/Sapphire Substrate with Excellent Electromechanical Coupling

SummaryIn this work, the shear horizontal surface acoustic wave (SH-SAW) resonators were demonstrated on 15° YX-LiNbO 3 /SiO 2 /sapphire (LiNbO 3 -on-sapphire, LNOS) substrate. Compared to the reported gigahertz SAW resonators based on piezoelectric heterogeneous substrates, the fabricated resonator in this work exhibits a state-of-the-art electromechanical coupling coefficient (k ² ) of 42.2%, a maximum Bode-Q (Q max ) of 1457 and an excellent figure of merit (k ² ×Q max ) of 615. Besides, several methods for suppressing transverse modes were implemented and compared. Tilted interdigital-transducers combined with the apodization technique can suppress the transverse modes more thoroughly while maintaining decent Q values. Overall, SAW devices based on the LNOS substrate have great potential for RF filters with low insertion loss, steep skirts, and wide bandwidth.