Intrinsically Switchable GHz Ferroelectric ScAlN SAW Resonators

This paper reports on the intrinsic switching of GHz ferroelectric scandium aluminum nitride (ScAlN) surface acoustic wave (SAW) resonators. The reversible switching was demonstrated on 22% and 30% ScAlN for frequencies in the 1–– 3 GHz range, with metal interdigitated transducers (IDTs) of widths $1 {\mu} \mathrm{m} -400$ nm patterned with electron-beam lithography. COMSOL simulations were used to model resonator programming, with ScAlN switching under the IDTs. The devices show strong resonances with a quality factor of 915 and a coupling coefficient of 0.98% at 1.35 GHz. Two-state switching of the resonator is demonstrated with single-sided pulses of ± 6 MV/cm, which demonstrates reversible on and off switching of piezoelectricity in ScAlN. Progressively larger switching pulses in the $\pm (2 -5)$ MV/cm range demonstrate multi-state switching of the SAW device by tracking the S-parameters and quality factor. The results presented in this paper open up pathways towards programmable signal processing and sensing using ferroelectric ScAlN.