FEM simulation of AlN thin layers on diamond substrates for high frequency SAW devices

AlN/Diamond structure is very promising for high frequency acoustic wave devices. In this paper, a comprehensive investigation of AlN/Diamond structure is presented using finite element method. The phase velocity and the coupling coefficient of the first two modes of SAWs for the AlN/Diamond structure are numerically analyzed and compared to experimental data. Close agreement between experimental and numerical results is obtained. Results show that the mode 1 (Sezawa mode) exhibits the largest coupling coefficient of 1.28% associated with a phase velocity of 9500 m/s. Additionally, the temperature coefficient of frequency (TCF) and the reflection coefficient (r) are studied. The simulation results show that for a zero TCF, a high phase velocity of 10,800 m/s associated with a coupling coefficient of 0.5% can be obtained. These results demonstrate that the AlN/Diamond structure can be used to design wide-band and temperature-compensated SAW devices. The dependence of SAW devices performance with the electrode height, metallization ratio and mass-loading is also investigated.