Analysis of 5−10 GHz Higher-Order Lamb Acoustic Waves in Thin-Film Scandium Aluminum Nitride

SummaryIn this work, we report a systematic analysis of acoustic waves in thin-film 30% scandium-doped aluminum nitride (ScAlN) between 5 and 10 GHz. Higher-order Lamb mode acoustic delay line (ADL) testbeds are implemented in ScAlN, surpassing the operation frequency of prior reported works. Transducers with different lateral wavelengths (λ) between 0.8 µm and 1.4 µm are fabricated in 500 nm thick sputtered ScAlN thin films. Key propagation characteristics, e.g., group velocity (vg) and acoustic propagation quality factor (Q), are experimentally studied for the first time for Lamé and first-order symmetric (S1) modes beyond 6 GHz. This work presents an approach to extract the intrinsic acoustic loss in piezoelectric thin films, guiding future frequency scaling of microacoustic devices into mm-wave bands.