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

Abstract

This paper presents the use of ferroelectric behavior in scandium–aluminum nitride (ScxAl1−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 (Sc0.28Al0.72N) 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 Sc0.28Al0.72N Lamb-wave resonators are promising candidates to realize single-chip multi-band reconfigurable spectral processors for radio-frequency front-ends of modern wireless systems.

Demonstration of compensated n-type scandium nitride Schottky diodes

“…Several strategies, such as alloying ScN with other heavy metal nitrides (such as NbN, CrN, etc) and ion-beam irradiation have been employed to reduce the thermal conductivity and increase ZT [26][27][28][29][30]. Solid solution alloys of ScN with wurtzite IIInitride semiconductors such as Al x Sc 1−x N, Ga x Sc 1−x N have also demonstrated high c-axis piezoelectric coefficient and are actively researched for resonators and bulk/surface acoustic wave devices in recent times [31][32][33][34].…”

Quasi-3D Model for Lateral Resonances on Homogeneous BAW Resonators

“…Spurious modes, particularly their cancellation, are essential considerations in BAW resonator design [1][2][3]. These spurious modes are primarily associated with the lateral propagation of Lamb waves within a resonator [4], which can be employed for designing novel resonant structures [5]. However, for devices like FBARs and SMR-BAW, these lateral effects pose significant challenges [6].…”

Editorial for Special Issue “Piezoelectric Aluminium Scandium Nitride (AlScN) Thin Films: Material Development and Applications in Microdevices”

“…In the last section, six papers address the fabrication and performance of various AlScN-based devices [ 12 , 13 , 14 , 15 , 16 , 17 ]. It has been recognized quite early in the development of AlScN that the etching rate drops dramatically compared to pure AlN, and the existing etching approaches used for group-III nitrides must be revised, especially when vertical side-wall geometry has to be well controlled.…”

“…Although the frequency, acoustic velocity, and electromechanical coupling were similar in both, the quality factor and figure of merit (FOM) were much higher, and insertion loss improved when using the single crystal diamond as a substrate. Finally, dual-mode Lamb wave resonators are demonstrated by Rassay et al [ 17 ]. Patterned molybdenum was used as a bottom electrode, where tapering enabled crack-free overgrowth by AlScN.…”