Analysis of longitudinal leaky surface acoustic wave propagation characteristics on a piezoelectric ScAlN layer/sapphire or quartz substrate

Abstract

Longitudinal leaky surface acoustic wave (LLSAW) modes with a high phase velocity are suitable for high-frequency SAW filter applications. However, their attenuation is higher than that of other SAW modes, causing a small Q factor. On the other hand, a low attenuation and high coupling factor K2 in LLSAWs on a piezoelectric thin plate/high-velocity sapphire or quartz substrate have been demonstrated theoretically and experimentally. We expected that LLSAWs propagating on a highly piezoelectric ScAlN layer/sapphire or quartz substrate also have a high phase velocity, high K2 and low attenuation. In this study, the characteristics of LLSAWs on ScAlN layer/sapphire or quartz substrates were theoretically investigated. The cut angle and SAW propagation direction of quartz substrates strongly affect the attenuation of LLSAWs on the layered structure. We found that a LLSAW resonator with (0° 90° 90°) Sc0.4Al0.6N layer/X-cut 30° Y propagation quartz has a high Q factor and high K2, which is adequate for SAW filter applications.

Enhancement of coupling factor in 0th to 4th mode Rayleigh surface acoustic waves on polarity inverted multilayered ScAlN film/AlN and BN substrates

“…Various SAW devices with ScAlN films/high phase velocity substrates have also been reported. [21][22][23][24][25][26][27] The K 2 for the 1st mode RSAW (=5.5%) on the IDT/ScAlN film/diamond substrate structure 21) was approximately 4.6 times higher than that for the IDT/AlN film/diamond substrate structure. The SAW on a polarity inverted ScAlN film structure was also studied for further enhancement of the K 2 for the 1st mode RSAW.…”

Analysis of Sezawa mode Rayleigh-type SAWs on ScAlN film/floated electrode layer/ScAlN film/high velocity substrates

“…Subsequently, various SAW devices using ScAlN film/high velocity substrate have been reported. [16][17][18][19][20] The K 2 of 5.5% in the Sezawa mode RSAW device of the IDT/ScAlN film/diamond substrate structure was approximately five times higher than that of the IDT/AlN film/diamond substrate structure. In addition, it has been theoretically found that the K 2 of the high-order mode RSAWs on wurtzite piezoelectric films/high velocity substrates can be further enhanced by using multilayer polarization reversal film structures.…”

Development and Application of SAW Filter

“…Tetsuya Kimura, Masashi Omura 2018 Apply the inter-digital transducer cycle of 3.5 GHZ utilizing IHP SAW to another new SAW device LLSAW [ 70 ], and the results show that good transducer performance can still be obtained in the 5 GHZ range. In 2019, Masashi Suzuki and Naoya Sawada found that LLSAW propagating on a high-voltage electrical ScAlN layer/sapphire or quartz substrate also has high phase velocity, high K2, and low attenuation [ 71 ].…”