High-frequency and high-temperature stable surface acoustic wave devices on ZnO/SiO2/SiC structure

The explosive growth of wireless communication and the creation of new frequency bands for 5G systems increasingly require surface acoustic wave (SAW) with high operating frequency (i.e. 3-6 GHz) as well as high-temperature stability. In this work, high-frequency and high-temperature stable SAW devices using ZnO/SiO2/SiC layered structures were proposed and reported. SAW characteristics of the Sezawa wave mode, including the phase velocities (V-p), electromechanical coupling coefficients (K-2) and temperature coefficient of frequency (TCF), were studied systematically by the finite element method. High-frequency SAW one-port resonators with the resonant frequency ranging from similar to 4.5-5.4 GHz were fabricated on the above structures. With SiC substrate providing high velocity and SiO2 interlayer for temperature compensation, a 5.0 GHz and nearly zero TCF of 0.7 ppm degrees C-1 can be achieved in a SAW device based on ZnO/SiO2/SiC structure. The good performance of these devices demonstrates that the ZnO/SiO2/SiC structure is promising for high-frequency and good temperature-stability SAW device applications.