High Qm×K2t intrinsically switchable BST thin film bulk acoustic resonators

A high Q_m×K²_t fundamental mode intrinsically switchable thin film bulk acoustic resonator (FBAR) based on Bao.sSro.sTiOa is designed and fabricated at 2 GHz. High Q_m×K²_t BST FBARs are required for the design of low insertion loss switchable BAW filters. Measurement results for the BST FBAR show a resonator mechanical quality factor (Q_m) of 360 with an electromechanical coupling coefficient (K²_t) of 8.6%. Q_m×K²_t is 30.8, and to the best of authors' knowledge, it is the highest among the previously reported switchable BST resonators. The measured temperature coefficients of frequency (TCF) for the series and parallel resonance frequencies are -65 and -68 ppm/K, respectively.