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

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Spurious modes (SMs) suppression and electromechanical coupling coefficient (kₜ^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 thekₜ^2without 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, thekₜ^2of the S1 mode has been increased to more than twice and thef× Q× kₜ^2of the device can reach up to1.08× 10^11Hz.