X-cut LiTaO3 on SiC Hetero-Substrate for High-Performance Longitudinal Leaky SAW Devices

Novel Wi-Fi technologies are expanding support to the less congested frequency band, such as the 7 GHz band. To obtain high-frequency surface acoustic wave (SAW) devices without narrowing the linewidth drastically, a novel X-cut LiTaO3/SiC hetero-substrate is proposed for developing the high-performance longitudinal leaky SAW (LL-SAW) devices. The demonstrated LL-SAW resonators exhibit scalable resonant frequencies from 6 to 8 GHz, in which a typical LL-SAW resonator operating at 7.15 GHz without spurious peaks exhibits a maximum quality factor (Bode-Qmax) of 1230. The fabricated LL-SAW filter shows a center frequency of 7.07 GHz, an insertion loss of 2.6 dB, and an out-of-band rejection greater than 25 dB over a wide frequency range. The 3-dB bandwidth is 116 MHz, which can be modulated by adjusting the propagation angle. This work underscores the immense potential and feasibility of LL-SAW filters on the X-cut LiTaO3/SiC substrate for advancing SAW devices in high-frequency applications.