AlScN-on-SiC Surface Acoustic Wave Resonators and Filters above 4 GHz

With the continuous rise of the carrier frequencies in wireless systems, new material and design strategies enabling frequency scaling for surface acoustic wave resonator technology are required. We report AlScN-on-SiC Sezawa SAW resonators with resonances above 4 GHz. In previously demonstrated AlScN-based SAW resonators, the effective electromechanical coupling coefficient (k2eff) limited the bandwidth potential. We show that by integrating a patterned floating bottom electrode, the transduction efficiency can be enhanced compared to standard, IDT-only architectures. With a floating bottom electrode, we demonstrate Sezawa SAW resonators achieving a k2eff of 10.8%. In addition, we experimentally demonstrate filters with center frequencies in the 5–6 GHz range with 4–5% fractional bandwidth and a minimum insertion loss of 1 dB.