5.8-GHz Coupled Shear SAW Resonator Based on Z-Cut LiNbO₃/SiO₂/Si Substrate

In this work, a new kind of coupled shear SAW (CS-SAW) resonator based on LiNbO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf>/SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>/Si substrate has been proposed and demonstrated. By designing and optimizing the interdigitated transducer (IDT) electrode geometries with respect to the piezoelectric thin-film layer thickness, two different shear piezoelectric coefficients, namely e<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15</inf> and e<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">16</inf>, were utilized in one mode of vibration, so that the electromechanical coupling coefficient (k<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>) was enhanced. The CS-SAW resonator operating at 5.8 GHz exhibits high k<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of 8.94% and Bode-Q<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</inf> of 120. This work not only achieves high performance of SAW resonators, but also discovers a new way of mode coupling.