C-Band Lithium Niobate on Silicon Carbide SAW Resonator With Figure-of-Merit of 124 at 6.5 GHz

In this work, we demonstrate a C-band shear-horizontal surface acoustic wave (SH-SAW) resonator with high electromechanical coupling ( ${k}_{\mathbf {t}}^{\mathbf {2}}$ ) of 22% and a quality factor (Q) of 565 based on a thin-film lithium niobate (LN) on silicon carbide (SiC) platform, featuring an excellent figure-of-merit (FoM $= {k}_{\mathbf {t}}^{\mathbf {2}}\cdot Q_{max}$ ) of 124 at 6.5 GHz, the highest FoM reported in this frequency range. The resonator frequency upscaling is achieved through wavelength ( $\lambda $ ) reduction and the use of thin aluminum (Al) electrodes. The LN/SiC waveguide and synchronous resonator design collectively enable effective acoustic energy confinement for a high FoM, even when the normalized thickness of LN approaches a scale of $0.5\lambda $ to $1\lambda $ . To perform a comprehensive study, we also designed and fabricated five additional resonators, expanding the $\lambda $ studied ranging from 480 to 800 nm, in the same 500 nm-thick transferred Y-cut thin-film LN on SiC. The fabricated SH-SAW resonators, operating from 5 to 8 GHz, experimentally demonstrate a ${k}_{\mathbf {t}}^{\mathbf {2}}$ from 20.3% to 22.9% and a Q from 350 to 575, thereby covering the entire C-band with excellent performance. [2024-0070]