  Surface Acoustic Wave (SAW) devices featuring Aluminum Scandium Nitride
(AlScN) on a 4H-Silicon Carbide (SiC) substrate, offer a unique blend of high
sound velocity, low thermal resistance, substantial piezoelectric response,
simplified fabrication, as well as suitability for high-temperature and harsh
environment operation. This study presents high-frequency SAW resonators
employing AlScN thin films on SiC substrates, utilizing the second SAW mode
(referred to as the Sezawa mode). The resonators achieve remarkable
performance, boasting a K2 value of 5.5% and a maximum Q-factor (Qmax) of 1048
at 4.7 GHz, outperforming previous benchmarks. Additionally, a SAW resonator
with a 960 nm wavelength attains 5.9 GHz frequency with record K2 (4.0%) and
Qmax (887). Our study underscores the potential of the AlScN on SiC platform
for advanced radio-frequency applications.
