High-Q Switchable BAW Resonators With 5-V Switching Voltages and Through GaN Vias

This article reports a gallium nitride (GaN)-based switchable bulk acoustic wave (BAW) resonator with low dc switching voltage and through GaN vias. The low switching voltages between “on” and “off” states are enabled by the control of the 2-D electron gas (2DEG) in AlGaN/GaN heterostructures via a vertical electric field. Direct electrical access to the bottom electrode through vias is formed in the proposed switchable BAW resonators. Compared to prior GaN BAW devices, this via-connected BAW device structure shortens the grounding path, reduces parasitics, and improves device performance. Besides, to avoid a deep GaN etch, the via-less switchable BAW resonator has also been developed for comparison. The via-connected resonators show measured Q over 730 at 2.4 GHz in the on state and with 5-V switching voltage, among the best-performed BAW resonators.