P3O-7 Theoretical Investigation of PSAW Generation and Propagation in AlN/Isotropic Diamond/Si Structure

Piezoelectric AlN films on isotropic diamond is a perspective technology for gigahertz-range acousto-electric devices. The attention of many investigators is attracted by the high velocities of SAW and PSAW modes in these structures and a number of experimental and theoretical works lend support to the validity of obtaining gigahertz-range electro-acoustic devices using micron technology. Most theoretical works, however, consider a simplified layered structure, namely, the AlN film on a semi-infinite diamond substrate. Even though the experimental velocities for SAW and PSAW modes agree rather well with the theoretical predictions, essential discrepancies were observed between predicted and experimental values in the generation efficiency of different acoustic modes in a given sample, as well as distortions in the interdigital transducers (IDT) response, which cannot be only explained in terms of acoustic wave velocity dispersion in the simplified layered structure. The experimental samples are usually implemented on more complex structures, including a Si substrate (isotropic or single crystal), a diamond layer (several acoustic wavelengths thick) and finally the AlN film. In this work we analyze these three-layered structures in order to explain the observed discrepancies and the results so obtained are compared with those calculated for the simpler AlN/diamond structure