High-Performance Acoustic Wave Devices on LiTaO<sub>3</sub>/SiC Hetero-Substrates
Liping Zhang, Shibin Zhang, Jinbo Wu, Pengcheng Zheng, Hongyan Zhou, Hulin Yao, Zhongxu Li, Kai Huang, Huarui Sun, Xin Ou
Abstract
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 ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> ), 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- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> of 8100 and an excellent TCF of −4.3 ppm/K, while the LL-SAW resonator presents a high Bode- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> of 1000 and an improved TCF of −25.4 ppm/K at 5.0 GHz. Besides, the demonstrated filters show the center frequencies ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{c}$ </tex-math></inline-formula> ) 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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{c}$ </tex-math></inline-formula> 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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{c}$ </tex-math></inline-formula> 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.