High-frequency surface acoustic wave resonator with ScAlN/ hetero-epitaxial diamond

High-frequency and wideband surface acoustic wave (SAW) devices have become an important topic in 5G communication systems and beyond. For this purpose, piezoelectric ScAlN thin films deposited on high SAW velocity diamond are studied in SAW resonators on the polycrystalline diamond (PCD) and hetero-epitaxial diamond (HED) substrates. A very strong c-axis orientation of ScAlN on HED was confirmed. Interdigital transducers of 0.8 mu m and 0.5 mu m were fabricated to realize 2.2 to 3.5 GHz high-frequency resonators. High Q values were obtained for the 2.3-2.5 GHz device on both PCD and HED. Additionally, a high electro-mechanical coupling coefficient (K-2) of 5.40-5.52% and high SAW velocities of 7400-7766 m/s were obtained in the 2.3-2.5 GHz devices. In comparison to the simulated coupling coefficient results of a previous report, ScAlN/diamond might have higher K-2 for the Sezawa wave.

Automated summary

Research has been conducted on the deposition of piezoelectric ScAlN thin films on high SAW velocity diamond for use in SAW resonators, achieving high-frequency resonance. The experiments showed a very strong c-axis orientation of ScAlN on HED, and high Q values were obtained for the 2.3-2.5 GHz devices on both PCD and HED.