Dual-Mode Scandium-Aluminum Nitride Lamb-Wave Resonators Using Reconfigurable Periodic Poling

This paper presents the use of ferroelectric behavior in scandium-aluminum nitride (Sc_xAl_1-xN) to create dual-mode Lamb-wave resonators for the realization of intrinsically configurable radio-frequency front-end systems. An integrated array of intrinsically switchable dual-mode Lamb-wave resonators with frequencies covering the 0.45-3 GHz spectrum. The resonators are created in ferroelectric scandium-aluminum nitride (Sc_0.28Al_0.72N) film and rely on period poling for intrinsic configuration between Lamb modes with highly different wavelengths and frequencies. A comprehensive analytical model is presented, formulating intrinsically switchable dual-mode operation and providing closed-form derivation of electromechanical coupling (kt2) in the two resonance modes as a function of electrode dimensions and scandium content. Fabricated resonator prototypes show kt2s as high as 4.95%, when operating in the first modes over 0.45-1.6 GHz, 2.23% when operating in the second mode of operation over 0.8-3 GHz, and series quality factors (Qs) over 300-800. Benefiting from lithographical frequency tailorability and intrinsic switchability that alleviate the need for external multiplexers, and large kt2 and Q, dual-mode Sc_0.28Al_0.72N Lamb-wave resonators are promising candidates to realize single-chip multi-band reconfigurable spectral processors for radio-frequency front-ends of modern wireless systems.