Acoustic Delay Lines in Thin-Film Lithium Niobate on Silicon Carbide

Abstract

This work demonstrates the first group of GHz low-loss and wideband acoustic delay lines (ADLs) using transferred Y-cut thin-film lithium niobate (LiNbO3) on silicon carbide (SiC) platform. Single-phase unidirectional transducers (SPUDT) in ADLs effectively excite shear horizontal surface acoustic wave (SH-SAW) with high electromechanical coupling (K <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) beyond 30%. The film stack confines the traveling acoustic wave in the piezoelectric layer with low propagation loss. SH-SAW ADL prototypes are built between 1.0 GHz and 2.7 GHz with delays between 3 ns and 1.04 μs. The prototypes achieve 3-dB fractional bandwidth (FBW) around 8% and minimum insertion loss (IL) between 2.5 dB and 5.7 dB. The acoustic propagation <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$Q$</tex> of SH-SAW in LiNbO3-on-SiC is extracted as around 2000 between 1 and 3 GHz, exceeding reported solidly mounted platforms so far. LiNbO3-on-SiC ADLs show great potential for RF and cross-domain applications at GHz.