Dual-Mode Hybrid Quasi-SAW/BAW Resonators With High Effective Coupling Coefficient

This article reports on a design journey for Sc_xAl₁ - N-based dual-mode hybrid quasi-surface and bulk acoustic wave (quasi-SAW/BAW) resonators. Four types of acoustic excitation configurations are proposed in these designs based on Sc_x Al_1-xN/6H-SiC stack architectures. The influence of Sc_x Al_1-xN materials, film thickness, and device configurations on the performance is investigated. After design optimization, the final dual-mode hybrid quasi-SAW/BAW resonators comprise of top electrode, partially etched Sc_x Al_1-xN pillars, and bottom electrode, which are stacked on a 6H-SiC substrate. The coupled quasi-SAW and BAW excited in the hybrid resonators enhance the resonance for both quasi-Rayleigh and quasi-Sezawa modes which results in a high effective coupling coefficient (K_eff²) and phase velocity ( v ). Simulation results show that the optimized hybrid quasi-SAW/BAW resonator based on Mo/Sc_0.4 Al_0.6N/Mo/6H-SiC configuration with SiO₂ filling the grooves has a remarkable K_eff² value of 14.55% and a high v above 7500 m/s, which make this kind of dual-mode hybrid quasi-SAW/BAW resonators have great potential in wideband and high-frequency applications.