A 5.3 GHz Al0.76Sc0.24N Two-Dimensional Resonant Rods Resonator with a kt2 of 23.9%

TL;DR

This paper reports a record-high electromechanical coupling coefficient of 23.9% in a 2D AlScN resonator, achieved through optimized fabrication and acoustic engineering, enabling advanced RF filtering applications.

Contribution

The work introduces a highly-doped AlScN 2DRR with unprecedented kt2, demonstrating potential for ultra-wideband RF filters in next-generation communication systems.

Findings

Record kt2 of 23.9% achieved in AlScN 2DRR

Enabled design of 5th-order ladder filters with 11% bandwidth

Potential for ultra-wideband RF filtering applications

Abstract

This work reports on the measured performance of an Aluminum Scandium Nitride (AlScN) Two-Dimensional Resonant Rods resonator (2DRR), fabricated by using a Sc-doping concentration of 24%, characterized by a low off-resonance impedance (~25 Ohm) and exhibiting a record electromechanical coupling coefficient (kt2) of 23.9% for AlScN resonators. In order to achieve such performance, we identified and relied on optimized deposition and etching processes for highly-doped AlScN films, aiming at achieving high crystalline quality, low density of abnormally oriented grains in the 2DRR's active region and sharp lateral sidewalls. Also, the 2DRR's unit-cell has been acoustically engineered to maximize the piezo-generated mechanical energy within each rod and to ensure a low transduction of spurious modes around resonance. Due to its unprecedented kt2, the reported 2DRR opens exciting scenarios towards the development of next generation monolithic integrated radio-frequency (RF) filtering components. In fact, we show that 5th-order 2DRR-based ladder filters with fractional bandwidths (BW) of ~11%, insertion-loss (I.L) values of ~2.5 dB and with >30 dB out-of-band rejections can now be envisioned, paving an unprecedented path towards the development of ultra-wide band (UWB) filters for next-generation Super-High-Frequency (SHF) radio front-ends.