15-GHz Epitaxial AlN FBARs on SiC Substrates
Wenwen Zhao, Mohammad Javad Asadi, Lei Li, Reet Chaudhuri, Kazuki Nomoto, Huili Grace Xing, James C. M. Hwang, Debdeep Jena
Abstract
Epitaxial AlN thin-film bulk acoustic resonators (FBARs) on SiC substrates with first-order thickness extensional modes of 15-17 GHz are demonstrated. For the 15 GHz epi-AlN FBARs, the quality factor <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{\textit {ma}{x}}\approx {443}$ </tex-math></inline-formula> , 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">${k}_{\textit {ef}{f}}^{{2}}\approx {2}.{3}\%$ </tex-math></inline-formula> , and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${f}\cdot {Q} \approx {6}.{65}~\textit {TH}{z}$ </tex-math></inline-formula> figure of merit achieved are among the highest in the Ku-band (12-18 GHz). A clean primary mode with a high quality factor enables such epi-AlN FBARs to be utilized in Ku-band acoustic filters with clean bands and steep rejection. Because such epi-AlN FBARs share the same SiC substrate and epitaxial growth as AlN/GaN/AlN quantum well high-electron-mobility-transistors (QW HEMTs), they are well suited for monolithic integration with HEMT low noise amplifiers (LNAs) and power amplifiers (PAs).