On the Coupling Coefficient of ScyAl1-yN-based Piezoelectric Acoustic Resonators

This work investigates the electromechanical coupling coefficient (k
_t
²
) attained by two available piezoelectric acoustic resonator technologies relying on Aluminum Scandium Nitride (Sc
_y
Al
_1-y
N) films to operate. In particular, by using a theoretical approach, we extracted the maximum k
_t
²
-value attainable, for different scandium-doping concentrations (from 0% to 40%), by Film-Bulk-Acoustic-Resonators (FBARs) and Cross-Sectional-Lamé-Mode Resonators (CLMRs). For the first time, we show how the use of higher scandium doping concentrations can render the k
_t
²
of CLMRs higher (35%) than the one attained by FBARs (28%). Such a unique feature renders CLMRs as ideal candidates to form lithographically defined resonators and filters for next-generation wideband radiofrequency (RF) front-ends.