NanoDay 2021 – Poster 22 – Dicheng Mo and Sushant Rassay


Dicheng Mo

Intrinsically Switchable RF Ferroelectric 22%ScAlN Bulk Acoustic Wave Resonators

Dicheng Mo and Sushant Rassay

Authors: Dicheng Mo, Sushant Rassay, Roozbeh Tabrizian

Faculty Mentor: Roozbeh Tabrizian, PhD

College: College of Engineering

Department: Electrical and Computer Engineering


The skyrocketing number of users and their booming data demand highlight the need for efficient use of wireless spectrum. Besides exploring new bands at higher frequencies, opting for dynamic spectrum allocation techniques is essential to enhance the efficiency of spectrum usage. Traditional RF front-end modules enable limited switchability or tuning through the use of multiple single-band filters/duplexers along with external switches. Being not only hard to scale down, the switches for filters targeting more new bands add excessive loss, interference, and latency. One solution is achieving intrinsical reconfigurable acoustic resonators and filters utilizing ferroelectricity or anti-ferroelectricity. However, for traditional materials like HZO or BST, their fabrication challenges and the less satisfying Q hinder their adoption at higher frequencies. One of the potential candidates is the recently discovered scandium aluminum nitride (ScAlN). In this presentation, we report on the intrinsic ferroelectric switchability of two-port scandium aluminum nitride RF bulk acoustic wave resonators. The ferroelectric behavior in 22% scandium-doped ScAlN enables switching in-plane and thickness-extensional BAW resonators through pulsed depolarization of the films. 445 MHz and 5.8 GHz 22% ScAlN resonator prototypes are presented with Qs exceeding 900 and insertion losses as low as -3dB. After multiple switching pulses, a ~15dB increase in S21 IL is measured at film depolarization and a 180° shift in the S21 phase with little IL change upon complete polarization reversal under the ports.


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