Increased electromechanical coupling in w−ScAlN
Gunilla Wingqvist, Ferenc Tasnádi, Agne Zukauskaite, Jens Birch, Hans Arwin, and Lars Hultman
The thin film electroacoustic technology and the use of wurtzite semiconductors (namely AlN) has established a sector within the piezoelectric industry, specifically through the release of the thin film bulk-acoustic resonator duplex filters for the use in mobile phones. AlN has proven to be a superior material due to high acoustic and dielectric quality and compatibility with the electronic circuit fabrication. However, a limiting factor of AlN, and hence the whole thin film electroacoustic technology as such, is its low electromechanical coupling factor of 6%–7%, which is the determining factor for bandwidth in filters.
We present the promise of superior electromechanical coupling, in w−ScAlN by studying its dielectric properties. w−ScAlN (0<Sc content<0.3) thin films grown by dual reactive magnetron sputtering exhibited low dielectric losses along with minor increased dielectric constant (epsilon). Ellipsometry measurements of the high frequency epsilon; showed good agreement with density function perturbation calculations. Our data show that the electromechanical coupling factor will improve from 7% to 10% by alloying AlN with up to 20 mol % ScN.
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Last updated: 11/22/10