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Materials 2015, 8(3), 1204-1212;

GaN Micromechanical Resonators with Meshed Metal Bottom Electrode

Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109, USA
Department of Photonic & Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan
Author to whom correspondence should be addressed.
Academic Editor: C. Lewis Reynolds
Received: 30 July 2014 / Revised: 13 February 2015 / Accepted: 12 March 2015 / Published: 17 March 2015
(This article belongs to the Special Issue Compound Semiconductor Materials 2014)
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This work describes a novel architecture to realize high-performance gallium nitride (GaN) bulk acoustic wave (BAW) resonators. The method is based on the growth of a thick GaN layer on a metal electrode grid. The fabrication process starts with the growth of a thin GaN buffer layer on a Si (111) substrate. The GaN buffer layer is patterned and trenches are made and refilled with sputtered tungsten (W)/silicon dioxide (SiO2) forming passivated metal electrode grids. GaN is then regrown, nucleating from the exposed GaN seed layer and coalescing to form a thick GaN device layer. A metal electrode can be deposited and patterned on top of the GaN layer. This method enables vertical piezoelectric actuation of the GaN layer using its largest piezoelectric coefficient (d33) for thickness-mode resonance. Having a bottom electrode also results in a higher coupling coefficient, useful for the implementation of acoustic filters. Growth of GaN on Si enables releasing the device from the frontside using isotropic xenon difluoride (XeF2) etch and therefore eliminating the need for backside lithography and etching. View Full-Text
Keywords: gallium nitride (GaN) microelectromechanical (MEMS) resonators; metal-organic chemical vapor deposition (MOCVD); epitaxial growth; piezoelectric gallium nitride (GaN) microelectromechanical (MEMS) resonators; metal-organic chemical vapor deposition (MOCVD); epitaxial growth; piezoelectric

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Ansari, A.; Liu, C.-Y.; Lin, C.-C.; Kuo, H.-C.; Ku, P.-C.; Rais-Zadeh, M. GaN Micromechanical Resonators with Meshed Metal Bottom Electrode. Materials 2015, 8, 1204-1212.

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