Intrinsically Switchable Ferroelectric Scandium Aluminum Nitride Lamb-Mode Resonators

Abstract

This letter reports intrinsically switchable ultra- and super-high-frequency Lamb-mode resonators based on the use of ferroelectricity in scandium aluminum nitride (ScxAl1−xN) films. Highly crystalline 200nm-thick Sc0.22Al0.78N film is sputtered using segmented-target reactive magnetron sputtering, and interdigitated electrodes are patterned to create one-port resonators operating in symmetric Lamb modes. The resonators are intrinsically switched using the ferroelectric behavior in Sc0.22Al0.78N film and through polarization switching at one of the terminals, resulting in a zero-sum electromechanical coupling factor ( ${k}_{t}^{2}$ ). Resonators with frequencies over 0.45 – 6 GHz, frequency $\times $ quality factor product ( ${f}_{s}\times {Q}$ ) as high as $4\times 10^{12}$ , and and $k_{t}^{2} \times Q$ product exceeding29 aredemonstrated. The intrinsic switchability of resonators is characterized using 100ms triangular monopolar pulses, resulting in an admittance switching isolation as high as 15dB.