High electro-mechanical coupling coefficient SAW device with ScAlN on diamond

In this study, Sc concentration dependence of Sc (x) Al1-x N/AlN/poly-crystalline diamond/Si surface acoustic wave (SAW) characteristics at high Sc from 23.8% to 44.3% was investigated by fabricating one-port SAW resonator at high frequency. 3.8 GHz one-port resonator fabricated on Sc0.43Al0.57N showed an excellent performance of electro-mechanical coupling coefficient (K (2)) as high as 6.34% for 2nd mode Sezawa wave, which enables a wide bandwidth in high frequency applications. The temperature coefficient of frequency was approximately -40 to -50 ppm deg(-1) for the device fabricated with Sc concentration of 42.9%. This is a smaller value compared to conventional high K-2 bulk materials such as LiNbO3. As the result, a high K-2 6.34% material system at a higher Sc concentration of ScAlN/AlN/PCD was found to be possible at a high phase velocity of 7000 m s(-1). Combined with the extremely high-power durability of diamond based device, high-power durable wideband SAW device at high frequency can be expected.