Miniature LiNbO3/SiO2/Si SH-SAW Resonators With Near-Spurious-Free Response

In this letter, we present an investigation into the design, simulation, and characterization of near-spurious-free shear horizontal surface acoustic wave (SH-SAW) resonators that utilize a short acoustic aperture (A) in a LiNbO
₃
/SiO
₂
/Si functional substrate. By forming a miniature design through reducing the aperture of the interdigital transducer (IDT) from 20 wavelengths (
$\lambda {)}$
to only
$2\lambda $
, we observed a significant reduction in the transverse resonance of the guided SH-SAW, while still retaining the maximum Bode-
${Q}$
(
${Q}_{{\textit {ma}{x}}}{)}$
. The proposed miniature resonators exhibit an excellent
${Q}_{{\textit {ma}{x}}}$
of 1,200 and an electromechanical coupling (
$\mathbf {k}_{{\text {eff}}}^{{{2}}}{)}$
of 25% at 1 GHz with thin gold (Au) electrodes. These properties led to a high figure-of-merit (FoM
_max
=
${k}_{{\text {eff}}}^{\mathbf {{2}}} \boldsymbol {\cdot }{Q}_{{\textit {ma}{x}}}{)}$
of 300. Using this technique, GHz SH-SAW resonators with miniaturized transducer capacitance
${C}_{o}$
down to 160 fF are also characterized with a high FoM
$_{\text {max}} >$
200. The implementation of such miniature resonators holds significant promise for emerging applications that demand a near-spurious-free response and scalable capacitance, such as RF impedance transformers and low power oscillators for ultra-low-power radios.