Analysis of a longitudinal leaky surface acoustic wave and its high-order modes on a rotated Y-cut 90°X-LiNbO₃/SiC bonded structure in the leaky region

Abstract The properties of a longitudinal leaky surface acoustic wave (LLSAW) on a rotated Y-cut 90°X-LiNbO 3 (LN)/4H-SiC bonded structure are theoretically investigated. A 70°Y90°X-LN thin plate is shown to exhibit the minimum attenuation at a normalized LN thin-plate thickness h / λ of 0.046 (λ: wavelength). Results of a finite-element simulation show spurious-free resonance properties, with a phase velocity exceeding 9500 m s −1 , an admittance ratio (AR) exceeding 60 dB, a Q factor exceeding 1000, and an effective electromechanical coupling factor ( K eff 2 ) of 2.2%–3.2% at a normalized Al electrode film thickness h Al / λ of 0.031–0.036 and h / λ = 0.07–0.09. Additionally, the resonance properties of higher-order LLSAW modes are also examined. Based on the results, the first-order mode exhibits spurious-free resonance properties, with a phase velocity of 11703 m s −1 , an AR of 61 dB, a Q factor exceeding 700, and a K eff 2 of 4.2% at h Al / λ = 0.08 and h/ λ = 0.19.