【Domestic Papers】Influence of temperature on the performance of ε-Ga₂O₃-based surface acoustic wave delay lines

      Researchers from the Sun Yat-sen University have published a dissertation titled "Influence of temperature on the performance of ε-Ga₂O₃-based surface acoustic wave delay lines" in ICAPMS 2025.

Project Support

      This work was supported by the National Key Research and Development Program (No. 2023YFF1500700), the Research and Development Plan Project of Guangdong Province (No. 2021B0101300005) and Guangdong Basic and Applied Basic Research Foundation (No. 2022B1515120081).

Background

      Nowadays, surface acoustic wave (SAW) devices have been extensively applied in temperature, chemistry, pressure, gas and microfluidics sensors. Traditional passive SAW sensors are based on two-port delay lines or single-port resonators, which are compatible with antennas to form a wireless system. Compared with other types of sensing, wireless SAW technology is an effective solution in some hostile environments, such as underground detection, remote telemetry and aerospace platforms. Today, SAW devices have been increasing adopted in various systems thanks to their miniaturized size, excellent sensitivity and stability.

      In this work, the propagation loss of ε-Ga₂O₃ is extracted from the scattering parameters of SAW delay lines. The temperature dependence of center frequencies, coupling coefficient (K²) and insertion loss are also studied. The experimental results demonstrate ε-Ga₂O₃ to be a promising contender for temperature sensing application.

Abstract

      With the mature advancement of wireless sensing, the requirements for highperformance surface acoustic wave (SAW) devices keeps booming. Epsilon-phase gallium oxide (ε-Ga₂O₃) has been identified as a promising semiconductor due to its wide bandgap and strong piezoelectricity. In this study, the propagation loss, coupling coefficient (K² ) and temperature coefficient of frequency (TCF) are extracted from the ε-Ga₂O₃-based SAW delay lines. The propagation loss of ε-Ga₂O₃ is extracted to be 0.04596 dB/λ at 1286 MHz for Rayleigh mode and 0.10986 dB/λ at 2083 MHz for firstorder Sezawa mode. The TCF of ε-Ga₂O₃ for Rayleigh mode and first-order Sezawa mode are determined to be -69.0~-60.0 ppm/℃ and -57.5~-50.1 ppm/℃, respectively. K ² of ε-Ga₂O₃ is extracted to be ~1.0%. Both K² and insertion loss of ε-Ga₂O₃-based SAW delay lines keep stably varying as the temperature rises to 100℃. The superior K² performance and good temperature stability indicate ε-Ga₂O₃ a promising material for application in high-performance temperature sensing systems.

Conclusions

      In this work, ε-Ga₂O₃-based SAW delay lines were fabricated with different free-space gaps. Propagation loss, TCF and coupling coefficient (K²) of the devices are extracted from scattering parameters. The propagation loss of Rayleigh mode is extracted to be 0.04596 dB/λ at 1286 MHz and for first-order Sezawa mode is 0.10986 dB/λ at 2083 MHz. The TCF of ε-Ga₂O₃ for Rayleigh mode and first-order Sezawa mode are determined to be -69.0~-60.0 ppm/℃ and -57.5~-50.1 ppm/℃. ε-Ga₂O₃ possesses a higher coupling coefficient K² (~1.0%) than the traditional AlN/sapphire structure (~0.2%) and exhibits excellent temperature stability. The insertion loss of ε-Ga₂O₃-based SAW delay lines keeps stably varying as the temperature rises to 100℃. The large enough TCF value, superior K² performance, and good temperature stability of ε-Ga₂O₃ make it a promising contender for application in highperformance temperature sensors.