High-Performance Acoustic Wave Devices on LiTaO3/SiC Hetero-Substrates

We present high-performance shear horizontal surface acoustic wave (SH-SAW) and longitudinal leaky SAW (LL-SAW) devices using lithium tantalate (LiTaO3) thin films on silicon carbide (SiC) substrate. The 4-in LiTaO3-on-SiC (LTOSiC) hetero-substrate was prepared by an ion-slicing process. Instead of the Si-based piezo-on-insulator substrates, generally embedded with functional dielectric layers (e.g., SiO2), LTOSiC with a simple structure has achieved exciting results on device frequency, quality factor ( $Q$ ), temperature coefficient of frequency (TCF), and thermal transport properties. The demonstrated resonators show the scalable resonances of 1.19–4.91 GHz, in which the gigahertz SH-SAW resonator exhibits an ultrahigh Bode- $Q$ of 8100 and an excellent TCF of −4.3 ppm/K, while the LL-SAW resonator presents a high Bode- $Q$ of 1000 and an improved TCF of −25.4 ppm/K at 5.0 GHz. Besides, the demonstrated filters show the center frequencies ( $f_{c}$ ) of 2.74–4.26 GHz, the insertion loss (IL) below 1.26 dB, and an out-of-band (OoB) rejection of 10–45 dB. The SH-SAW-based filter shows a $f_{c}$ of 3.36 GHz, an IL of 0.78 dB, and a 3-dB bandwidth of 180 MHz, while the LL-SAW-based filter shows a $f_{c}$ of 3.85 GHz and an IL of 0.85 dB. Overall, LTOSiC may serve as an advanced material platform of acoustic devices for 5G-frequency range 1 (5G-FR1) bands.