Spurious-Free S₁ Mode AlN/ScAlN-Based Lamb Wave Resonator With Trapezoidal Electrodes

Spurious modes (SMs) suppression and electromechanical coupling coefficient ( ${k}_{t}^{{2}}$ ) improvement in Lamb wave resonators (LWRs) have always been the research hotspot. In this work, a 2.5 GHz spurious-free S1 mode AlN/ScAlN-based LWR with trapezoidal electrodes is proposed. The AlN/Sc0.096AlN composite film is prepared by Physical Vapor Deposition (PVD) to improve the ${k}_{t}^{{2}}$ without numerous abnormal grains. Measured results show that the SMs are effectively suppressed over a wide frequency range (1.5–3.5 GHz). Relying on the using of AlN/Sc0.096AlN composite film and the elimination of SMs, the ${k}_{t}^{{2}}$ of the S1 mode has been increased to more than twice and the ${f}\times {Q}\times {k}_{t}^{{2}}$ of the device can reach up to ${1}.{08}\times {10}^{{11}}$ Hz.