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

Abstract

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 Vp, the electromechanical coupling coefficients K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , and quality factors Q of one-port SAW resonators have been studied considering various ZnO normalized thicknesses h/λ. The resonators with large K2 and high Q are implemented over 5-7 GHz demonstrating K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of 0.47%-2.83% and Q of 146-549. Specifically, a high K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of 2.83% and a large Q of 549 are simultaneously achievable for the resonator at 5.19 GHz. Finally, with the high Vp of ZnO/SiC structure being up to 6800 m/s at h/λ = 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.