AlN/ScAlN composite films-based spurious free A1 mode lamb wave resonator with adjustable effective electromechanical coupling coefficient

Abstract

Abstract Narrow-band filters are widely applied in the narrow-band Internet of Things (NB-IoT). To meet the diverse bandwidth requirements of NB-IoT applications, this work presents the first antisymmetric (A1) mode Lamb wave resonators (LWRs) based on aluminum nitride (AlN) and AlN/ScAlN composite films. The impact of structural parameters, including pitch (P) and duty factor (DF), on main mode excitation and suppression of spurious modes is investigated. The optimal P and DF are found to be 10 μm and 0.05, respectively. Based on spurious-free A1 LWRs, an AlN/Sc0.096Al0.904N composite film is utilized to adjust the effective electromechanical coupling coefficient k eff 2 . The experiment results demonstrate a tunable k eff 2 from 0.40% (5 MHz) to 0.25% (3 MHz), realizing a 37.5% adjustment range of k eff 2 , which establishes a foundation for narrow-band tunable filters.