Potential of Al2O3/GaN/Sapphire layered structure for high temperature SAW sensors

This paper describes the investigation of the potential of packageless structures for acoustic wave sensor applications based on Al₂O₃/IDT/GaN/Sapphire structure. The finite elements modeling predicts the possibility of acoustically isolated waveguiding layer acoustic wave (WLAW) to propagate inside this structure with very low displacement at the top surface of the topmost Al₂O₃ layer. This layer serves as a protecting layer against oxidation of internal layers as well as an acoustically isolating layer, providing a mean for packageless packaging of this structure. The modeling results get confirmation in experiments with the precursor IDT/GaN/Sapphire structure thus supporting hopes on the predicted correct operation of the final Al₂O₃/IDT/GaN/Sapphire structure.