Electromechanical coupling and gigahertz elastic properties of ScAlN films near phase boundary

Abstract

The electromechanical coupling, elastic properties, and temperature coefficient of elastic constant c 33 D of ScxAl(1-x)N films with high Sc concentration (x) of 0-0.70 were experimentally investigated. Near the phase boundary, a Sc0.41Al0.59N film exhibited a maximum thickness extensional mode electromechanical coupling coefficient kt2 of 12% (kt = 0.35), which is almost double the value of 6.4% for typical pure AlN films. In the region of 0 < x < 0.2, the electromechanical coupling was confirmed to increase without any detectable deterioration in the temperature stability of c 33 D (=-54.5 ppm/ °C). This region is favorable in terms of temperature stability and is suitable for wideband resonator filter applications.