High-Frequency Surface Acoustic Wave Devices Based on ZnO/SiC Layered Structure

In this letter, highly (0002) oriented ZnO piezoelectric films were deposited on high acoustic velocity SiC substrates. Surface acoustic wave (SAW) devices on ZnO/SiC layered structure operating in the fundamental mode with high frequency to the 7-GHz range were successfully fabricated for the first time. The comprehensive experimental and theoretical investigations about phase velocities {V}_{p} , the electromechanical coupling coefficients {K}^{{2}} , and quality factors Q of one-port SAW resonators have been studied considering various ZnO normalized thicknesses {h}/\lambda . The resonators with large {K}^{{2}} and high Q are implemented over 5-7 GHz demonstrating {K}^{{2}} of 0.47%-2.83% and Q of 146-549. Specifically, a high {K}^{{2}} of 2.83% and a large Q of 549 are simultaneously achievable for the resonator at 5.19 GHz. Finally, with the high {V}_{p} of ZnO/SiC structure being up to 6800 m/s at {h}/\lambda = {0.14} , a 6.8-GHz SAW filter was achieved. Our work shows that the ZnO/SiC structure is of great potential for high-frequency SAW devices application.