Intrinsically Switchable Ferroelectric Scandium Aluminum Nitride Lamb-Mode Resonators

This letter reports intrinsically switchable ultra- and super-high-frequency Lamb-mode resonators based on the use of ferroelectricity in scandium aluminum nitride (Sc
_x
Al
_1-x
N) films. Highly crystalline 200nm-thick Sc
_0.22
Al
_0.78
N 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 Sc
_0.22
Al
_0.78
N 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 × quality factor product ( f
_s
×Q) as high as 4×10
¹²
, and and k
_t
²
×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.