Thick aluminum nitride contour-mode resonators mitigate thermoelastic damping

We demonstrate that the use of thick AlN films in Very-High-Frequency (VHF) contour-mode resonators (CMRs) enables a reduction of thermoelastic damping (TED) occurring in the metallic layers sandwiching the AlN film. This technique leads to a large improvement of the device quality factor (Q increase >72%) with respect to thin-film counterparts, resulting into the highest Q ever measured in air (4980) for CMRs operating in the same frequency range. This novel approach to reduce TED in AlN CMRs simultaneously enables a similar Q but a five times larger kt2 than previously demonstrated AlN resonators using electrodes suspended over the AlN film.