Surface Acoustic Wave Resonators Using a Novel ε-Ga2 O3 Piezoelectric Film Grown on Sapphire

This letter reports the demonstration of surface acoustic wave (SAW) resonators based on a novel $\varepsilon $ -Ga2O3 piezoelectric semiconductor. A 1- $\mu \text{m}$ thick phase-pure $\varepsilon $ -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 ( $\lambda $ ) of $2.4 \mu \text{m}$ . 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 ( ${V}_{p}$ ), the electromechanical coupling coefficients ( $K^{{2}}$ ) and the quality factors ( ${Q}$ ) 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 $\varepsilon $ -Ga2O3 piezoelectric semiconductor.