Enhancement of GHz electromechanical coupling coefficient ${k_{\mathrm{t}}}^{2}$ of MgZnO and CaZnO thin film BAW resonators

Electromechanical coupling coefficient kt
²
of MgZnO and CaZnO thin films in the UHF frequency ranges have not been reported. In this study, the relationship between kt
²
and dopant concentration of MgZnO and CaZnO thin films was investigated. In addition, longitudinal wave velocity VL of the MgZnO and CaZnO thin films was estimated. It has been found that kt
²
and VL of MgZnO increases with increasing Mg concentration. With respect to CaZnO, kt
²
increases, whereas VL decreases with increasing Ca concentration.