Boosting Performance ε -Ga 2 O 3 SAW Resonators With Mo Interlayer: Optimized Electric Field and Enhanced FOM

This letter reports a high-performance surface acoustic wave (SAW) resonator that incorporates a Mo interlayer between sapphire substrate and$\varepsilon $-Ga2O3(002). In this design, a Mo metal layer is used as the bottom electrode, followed by the deposition of an epitaxial$\varepsilon $-Ga2O3piezoelectric film via metal-organic chemical vapor deposition (MOCVD) and subsequent etching to expose the bottom electrode. Devices with the grounded Mo electrode achieve a figure of merit (FOM = effective electromechanical coupling coefficient$k^{2}_{\mathrm {eff}} \times $quality factor$Q$) enhanced by more than 60 times (from a maximum of 3.11 to 196) compared to conventional configurations. Finite element simulations indicate that the grounding bottom electrode optimizes the electric field distribution and prevents electric field leakage into the sapphire substrate, thereby boosting the FOM of the$\varepsilon $-Ga2O3-based SAW resonator. The proposed novel$\varepsilon $-Ga2O3SAW resonator structure significantly improves device performance and greatly enhances its potential for sensor applications.