BPZT HBARs for bias-tunable, stress generation at GHz frequencies

TL;DR

This paper demonstrates that BPZT-based HBARs can efficiently generate tunable acoustic waves up to 15 GHz, showing potential for high-frequency stress transduction despite traditional assumptions of dielectric losses in PZT.

Contribution

It provides the first experimental validation of GHz-frequency operation of BPZT HBARs with voltage tunability and quantifies their piezoelectric properties, advancing high-frequency piezoelectric device technology.

Findings

BPZT HBARs operate up to 15 GHz

Piezoelectric coefficient ~60 pm/V matches low-frequency values

Voltage tunability enhances device functionality

Abstract

The high frequency performance of strong piezoelectric materials like PZT remains relatively less explored due to the assumption of large dielectric/ferroelectric losses at GHz frequencies. Recently, the advent of magnetoelectric technology as an on-chip route to excite magnetization dynamics has provided the impetus to evaluate the electromechanical performance of PZT at microwave frequencies. In this work, we demonstrate that HBARs fabricated using Barium-doped PZT (BPZT) films can efficiently generate acoustic waves up to 15 GHz. The ferroelectricity of BPZT endows added functionality to the resonator in the form of voltage tunability of the electromechanical performance. We extract the piezoelectric coefficient by numerically comparing the performance of BPZT with the Mason model. The extracted piezoelectric coefficient ~60 pm/V agrees well with reported values on thin film PZT measured at low frequencies (<100 MHz). Our results suggest that with further improvement in device design and material processing, BPZT resonators could operate as large amplitude, tunable stress transducers at GHz frequencies.