Effect of Polarity of LiTaO3 and Quartz on Hetro Acoustic Layer Surface Acoustic Wave Properties

We developed advanced surface acoustic wave (SAW) devices so-called Hetero Acoustic Layer (HAL) SAW devices by combining thin LiTaO
3
(LT) and rot.Y90°X quartz (Qz). High impedance (Z) ratio over 80 dB, near-zero TCF and spurious-free characteristics up to 14 GHz have been achieved. In the previous study, we theoretically investigated the performance dependence on the polarity of LT and Qz. Bandwidth (BW) and Z ratio of HAL SAW resonators with four combinations of the polarity of 10-50°YX LT and 42°45’Y90°X Qz, +LT−/ +Qz−, + LT−/ −Qz, −LT+/ +Qz−, and −LT+/ −Qz, were calculated. The combinations of −LT+/ +Qz− and −LT+/ −Qz+ exhibit wider BW and higher Z ratio than +LT−/ +Qz− and +LT−/ −Qz+. In this study, we experimentally confirmed the BW and the Z ratio dependence on the polarity of 42°YX LT and 60°Y90°X Qz. In addition, we discuss the combinations of LT and Qz crystallographically equivalent to the combination.