BPZT HBARs for Magnetoelastic Stress Generation at GHz Frequencies

The high-frequency performance of strong piezoelectric materials like Pb(Zr_1-xTi_x)O₃ (PZT) remains relatively less explored due to the assumption of large dielectric/ferroelectric losses at gigahertz (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 article, we demonstrate that high-overtone bulk acoustic resonators 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 approximately 60 pm/V agrees well with reported values on a 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.