Figure 7. Measured results and comparison with theoretical models.

(a) Relative improvement in Q_m for multiple resonators as a function of frequency and modeled N for four GaN wafers. Planar projections indicate the trends with respect to frequency for a fixed set of material properties (Wafer A). (b) Relative improvement in experimentally measured and extracted Q_m for four BAW resonators concurrently fabricated on Wafer A (and thus possessing the same material properties). As predicted by the model, increasing the resonance frequency (ω → ω_max) increases the relative improvement in Q_m. As expected from the model, increasing electron concentration reduces piezoelectrically coupled phonon-electron interactions due to screening, and leads to (c) a higher nominal f × Q (lower loss) but also (d) a lower relative acoustoelectric improvement in Q_m.