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The authors have investigated the influence of growth temperature and scandium concentration on the piezoelectric response of scandium aluminum nitride (ScxAl1−xN) films prepared by dual reactive cosputtering. The piezoelectric response strongly depends on the growth temperature and scandium concentration. The piezoelectric response of the films prepared at 400 °C gradually increases with increasing scandium concentration. On the other hand, the piezoelectric response of the films prepared at 580 °C drastically decreases and increases in the scandium concentration from 30% to 40%. We think that the drastic change of the piezoelectric response is due to the disordered grain growth.

This paper describes application of Sc-doped AlN (ScAlN) to wideband SAW devices in the 1 to 3 GHz range. First, it is shown theoretically that large SAW velocity and electromechanical coupling factor are simultaneously achievable when the ScAlN film is combined with a base substrate with extremely high acoustic wave velocities, such as diamond and SiC. Next, SAW delay lines are fabricated on the ScAlN/6H-SiC structure, and reasonable agreement between the theory and experiment is obtained. Finally, one-port SAW resonators are fabricated on the structure, and it is shown that high-performance is achievable in the 1 to 3 GHz range by use of the structure.

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