Surface Acoustic Wave Resonators Using a Novel ε-Ga<sub>2</sub> O<sub>3</sub> Piezoelectric Film Grown on Sapphire
Yujia Tu, Weiqu Chen, Zhipeng Zhang, Zimin Chen, Yanli Pei, Gang Wang, Xing Lü
Abstract
This letter reports the demonstration of surface acoustic wave (SAW) resonators based on a novel <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varepsilon $ </tex-math></inline-formula> -Ga2O3 piezoelectric semiconductor. A 1- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> thick phase-pure <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varepsilon $ </tex-math></inline-formula> -Ga2O3 film was heteroepitaxially grown on sapphire by metal organic chemical vapor deposition (MOCVD) and fabricated into a single-port SAW resonator with a wavelength ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula> ) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.4 \mu \text{m}$ </tex-math></inline-formula> . Two distinct resonate frequencies at 1.36 and 2.29 GHz were clearly observed, which were identified as the propagation of Rayleigh and Sezawa waves, respectively, through a finite element method (FEM) simulation of the displacement mode shapes. In addition, the phase velocities ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{p}$ </tex-math></inline-formula> ), the electromechanical coupling coefficients ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K^{{2}}$ </tex-math></inline-formula> ) and the quality factors ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}$ </tex-math></inline-formula> ) of the fabricated device have been studied for the two resonate modes. The results pave the way for the development of novel acoustic devices based on emerging <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varepsilon $ </tex-math></inline-formula> -Ga2O3 piezoelectric semiconductor.