Surface Acoustic Wave Devices Using Lithium Niobate on Silicon Carbide

This work demonstrates a group of shear horizontal (SH0) mode resonators and filters using lithium niobate (LiNbO3) thin films on silicon carbide (SiC). The single-crystalline X-cut LiNbO3 thin films on 4H-SiC substrates have been prepared by ion-slicing and wafer-bonding processes. The fabricated resonator has demonstrated a large effective electromechanical coupling (k(2)) of 26.9% and a high-quality factor (Bode-Q) of 1228, hence resulting in a high figure of merit (FoM = k(2) center dot Bode-Q) of 330 at 2.28 GHz. Additionally, these fabricated resonators show scalable resonances from 1.61 to 3.05 GHz and impedance ratios between 53.2 and 74.7 dB. Filters based on demonstrated resonators have been demonstrated at 2.16 and 2.29 GHz with sharp roll-off and spurious-free responses over a wide frequency range. The filter with a center frequency of 2.29 GHz shows a 3-dB fractional bandwidth of 9.9%, an insertion loss of 1.38 dB, an out-of-band rejection of 41.6 dB, and a footprint of 0.75 mm(2). Besides, the fabricated filters also show a temperature coefficient of frequency of -48.2 ppm/degrees C and power handling of 25 dBm. Although the power handling is limited by arc discharge and migration-induced damage of the interdigital electrodes and some ripples in insertion loss and group delay responses are still present due to the transverse spurious modes, the demonstrations still show that acoustic devices on the LiNbO3-on-SiC platform have great potential for radio-frequency applications.