Effect of change in piezoelectric layer thickness in high-overtone bulk acoustic resonator

High overtone bulk acoustic wave resonator (HBAR) employing piezoelectric thin films were designed and the effect of the crucial piezoelectric layer thickness on the resonator characteristics were studied. Numerical simulation is carried out for two different kinds of HBAR with two different Piezoelectric-films on a YAG substrate. By studying the frequency spectra of HBAR and finding the parallel and series resonances frequencies for different modes, the effective electromechanical coupling factor distribution and the spacing of parallel resonance frequency (SPRF) distribution for different modes are plotted with a variation of the Piezoelectric-film thickness keeping the substrate thickness as constant. Results indicate that with decrease in Piezoelectric-film thickness, the resonance frequency shifts towards a higher frequency range and the parallel resonance spacing increases but suffers decrease in the effective electromechanical coupling factor (k_eff²).