Electrically tunable film bulk acoustic resonator based on Au/ZnO/Al structure

An electrically tunable Au/N-ZnO/ZnO/Al film bulk acoustic resonator (FBAR) is proposed. The stack resonator is Au-piezoelectric ZnO layer-Al while Schottky diode junction is Au/N-ZnO semiconductor layer. The FBAR's resonance frequency changes as the junction capacitance decreases with reverse bias. Our experiments gave a frequency shift of ∼30 kHz/V at 1.46 GHz, maximum insertion loss ∼0.7 dB, and a very high Q factor above 1200. Circuit simulations indicated a tunable range of ∼3.8 MHz from optimizing the FBAR's structure and doping concentration of N-ZnO. Electrical tunability decreases from 27 kHz/V to 1.5 kHz/V with temperatures from 30 °C to 105 °C.