Spurious-Free S₁ Mode AlN/ScAlN-Based Lamb Wave Resonator With Trapezoidal Electrodes
Tiancheng Luo, Qinwen Xu, Zhiwei Wen, Yuanhang Qu, Jie Zhou, Binghui Lin, Yao Cai, Yan Liu, Chengliang Sun
Abstract
Spurious modes (SMs) suppression and electromechanical coupling coefficient ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${k}_{t}^{{2}}$ </tex-math></inline-formula> ) improvement in Lamb wave resonators (LWRs) have always been the research hotspot. In this work, a 2.5 GHz spurious-free S1 mode AlN/ScAlN-based LWR with trapezoidal electrodes is proposed. The AlN/Sc0.096AlN composite film is prepared by Physical Vapor Deposition (PVD) to improve the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${k}_{t}^{{2}}$ </tex-math></inline-formula> without numerous abnormal grains. Measured results show that the SMs are effectively suppressed over a wide frequency range (1.5–3.5 GHz). Relying on the using of AlN/Sc0.096AlN composite film and the elimination of SMs, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${k}_{t}^{{2}}$ </tex-math></inline-formula> of the S1 mode has been increased to more than twice and the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${f}\times {Q}\times {k}_{t}^{{2}}$ </tex-math></inline-formula> of the device can reach up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${1}.{08}\times {10}^{{11}}$ </tex-math></inline-formula> Hz.