Low Propagation Loss X-Band Impedance Matched Lamb Mode Delay Lines in 30% Scandium Aluminum Nitride

This work presents the first X-band operating Acoustic Delay Lines (ADL) in 30% Sc-doped Aluminum Nitride (ScAIN) employing a Cross-sectional Lamé Mode of vibration. Devices operating at 8.3, 9.4, and 10.15 GHz, impedance matched to 50, 200, and 500 Ω, and relying on a single top electrode excitation were designed and fabricated on a high-crystallinity piezoelectric thin film. The delay lines exhibit low propagation loss, as well as phase velocities closely matching the values extracted from finite element modeling simulations. The propagation loss is also used to compute the mechanical quality factor of the film in a broad frequency range, confirming its excellent piezoelectric properties and the potential of the Cross-sectional Lamé Mode of vibration to be frequency-scaled well beyond the sub-6 GHz band of 5G.