Acoustic Delay Lines in Thin-Film Lithium Niobate on Silicon Carbide
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 (K²) 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 Q 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.