Electromechanical Coupling Enhancement in A1 Mode Acoustic Resonators with Bi-Layer Structure

This work reports A1 mode acoustic resonators with bi-layer structure consisting of a Y128° LiNbO 3 thin film and a AlN coating layer. Through comparative experiments, electromechanical coupling enhancement effect was demonstrated in the bi-layer based A1 mode devices for the first time, and a large k ² t increment of 4.0% is obtained. Besides, the Q-factors and phase velocities of the resonators based on bi-layer structure are significantly boosted. The heat dissipation of the proposed A1 mode devices is also improved in simulations. The reported resonators potentially provide a filtering solution with larger fractional bandwidth (FBW), higher frequency, lower insertion loss (IL) and higher power handling to 5G front-ends.