Switchable and tunable resonators with barium strontium titanate on GaN/Sapphire substrates

A solidly mounted tunable barium strontium GaN/Sapphire substrate using a metalorganic solution deposition (MOSD) technique. An acoustic Bragg reflector was first formed on the GaN/sapphire substrate consisting of alternating layers of silicon dioxide and tantalum oxide deposited using a-spin on technique. Lower and upper electrodes were fabricated using sputter deposited platinum. The resonant frequency of the resonator could be tuned from 5.17 GHz to 5.20 GHz by applying a voltage of 8 V, resulting in tunability of about 0.6%. The quality factor of the resonator was found to depend on the applied voltage, with a maximum quality factor of 216 observed for an applied bias voltage of 8 V. The effective electromechanical coupling coefficient (kt²) of the resonator was found to be 13.1% at 8 V.