Achieving both high electromechanical response and stable temperature behavior in Si/SiO2/Al/LiTaO3 sandwich structure

In order to realize the following two goals including high electromechanical coupling coefficient (K2) and zero temperature coefficient of frequency (TCF) in a surface acoustic wave (SAW) device, the propagation characteristics of shear-horizontal type (SH-type) boundary waves in the Si/SiO2/Al/LiTaO3 “sandwich” structure are investigated by the three dimensional (3D) finite element method (FEM). The influences of layer SiO2 with different thickness (h) on the SH-type boundary waves characteristics, including the phase velocity (vp), reflection coefficient (kp), K2 and TCF, are theoretically analyzed. The results present that the SH-type boundary wave has a maximum K2 of 4.45% at h/λ=0.62 and has a zero TCF by adjusting h/λ to 0.69. Owing to the acoustic energy distribution approaching to the SiO2/LiTaO3 boundary, the size of Love wave based devices can be reduced to a few wavelength thickness of Si and 36°YX- LiTaO3 crystals, and which also give an opportunity to be integrated onto one chip with subsequent electronic circuits.