Development and Study of Composite Acoustic Resonators with Al/(Al, Sc)N/Mo/Diamond Structure with a High Q Factor in the UHF Range

Abstract

The paper demonstrates for the first time the possibility of using aluminum nitride–scandium as an effective piezoelectric material in composite acoustic resonators on synthetic diamond substrates. Composite resonators based on an Al/(Al, Sc)N/Mo/(100) diamond piezoelectric layered structure with three Sc concentrations have been studied in the frequency range of 0–20 GHz. It is shown that such resonators can be excited in a wide frequency range from 0.2 to 20 GHz with Q factors relatively on par with similar devices using pure aluminum nitride. The quality parameter Qf ≈ 3 × 10¹⁴ Hz in a resonator sample based on the Al/Al_0.7Sc_0.3N/Mo/(100) diamond structure is comparable to the similar record value for composite resonators on diamond substrates and thin-film piezoelectric AlN transducers. The maximum values of the squared effective electromechanical coupling coefficient for composite BAW resonators increased by almost an order of magnitude upon replacing an AlN with an ASN film.