Analysis of propagation and resonance properties of longitudinal leaky surface acoustic wave on LiNbO₃/SiC bonded structure

The propagation and resonance properties of longitudinal leaky surface acoustic waves (LLSAW) on a bonded structure comprising an X-cut LiNbO 3 (LN) thin plate and a 4H-SiC support substrate were theoretically investigated. Strong LLSAW responses with high Q factors were obtained at the LN thin-plate thickness h where the LLSAW phase velocity was slower than the bulk shear wave of 4H-SiC of 7126 m s −1 , and fractional bandwidth (FBW) of 9%–10% was obtained for Al film thickness normalized by wavelength of h Al / λ = 0.06–0.07 and h / λ = 0.30–0.40. Moreover, even at h / λ with a faster phase velocity than the bulk shear wave of 4H-SiC, strong LLSAW responses without spurious response owing to the LLSAW higher-order mode were obtained. Finally, h Al / λ = 0.031 and h / λ = 0.19 were determined to obtain a phase velocity of 7800 m s −1 , high Q factors, and FBW of 7.6%.