High-overtone bulk acoustic wave resonator on galliumnitride

In our previous research we already demonstrated micro acoustic devices, such as membrane based thin film bulk acoustic shear wave resonators and surface acoustic shear wave resonators, based on metal-organic-vapour-phase-epitaxial (MOVPE) grown highly oriented a-plane piezoelectric material. Although MOVPE is a well established process for compound semiconductor layer growth especially of III-V semiconductors as InP, GaAs, and the nitrides GaN or AlN as also design and simulation of micro acoustic devices is nowadays a well established knowledge, the linkage between both is quite a technological challenge. Using an adapted MOVPE growth process for a-plane GaN on r-plane sapphire with a process linked improved surface quality; the challenge to build up high-overtone bulk acoustic wave resonators (HBAR) with a shear polarization of the acoustic wave was risen within this research. Different designs of MEMS-based prototypes of HBARs were processed on a-plane GaN after intensive simulations, their acoustic electrical behaviour analyzed and the temperature coefficient of frequency determined.