52 GHz Surface Acoustic Wave Resonators in Thin Film Lithium Niobate on Silicon Carbide

This paper reports a surface acoustic wave (SAW) resonator at 52 GHz with a high quality factor (
Q
) of 188 and a high phase velocity of 12.2 km/s, marking the first millimeter wave (mmWave) SAW devices with high
Q
. Transferred 300 nm 128Y lithium niobate (LN) thin film on 4H silicon carbide (SiC) substrate is used for the acoustic platform. The dramatic frequency scaling is enabled by the high phase velocity thickness-shear mode, confined in the LN-SiC stack, thanks to the high stiffness and acoustic velocity of SiC. The high phase velocity of 12.2 km/s is approaching the longitudinal wave velocity of 12.5 km/s in 4H SiC. The resonator achieves electromechanical coupling (
k
²
) of 0.5%, 3-dB series resonance
Q
(
Q_s
) of 12, 3-dB shunt resonance
Q
(
Q_p
) of 188, and maximum Bode
Q
of 154. Upon further development, the mmWave solidly mounted acoustic platform could enable various applications in signal processing, optomechanical, and quantum applications.