Electrical Performances of a Surface Acoustic Wave Device With Inter-Digital Transducers Electrodes in Local Resonances

In this paper, we investigate numerically the coupling of the Rayleigh mode with the micro-wall resonance modes in inter-digital transducers (IDTs) electrodes of surface acoustic wave (SAW) devices. We perform a finite element analysis (FEA) of the SAW features using an implemented model using comsol Multiphysics^® software. The SAW structure comprises identical transmitter and receiver IDTs electrodes, with different electrode heights (h_e). The proposed FEA study is based on the extraction of reflection (S₁₁) and transmission (S₂₁) coefficients of the SAW device. The IDTs are considered to be a micro-wall phononic crystal acting as local resonators at frequencies inside the SAW passband. The locally resonance gap is strongly dependent on the h_e value, and S₁₁ and S₂₁ parameters are affected by the SAW energy absorption in the IDTs system. We have chosen two h_e values (0.5 and 3 µm) to study low and high aspect ratios of micro-walls, corresponding respectively to Bragg-type and resonance-type bandgaps appearing near the SAW central frequency. At the SAW resonance frequency, the return (S₁₁) and the insertion (S₂₁) losses are reduced. S₂₁ is reduced by 12.73 and 18.49 dB for h_e = 0.5 and 3 µm, respectively, accompanied by an increase in the quality factor, and S₁₁ parameter is reduced by 1.357 and 4.98 dB for h_e = 0.5 and 3 µm, respectively.