Observation of the acoustoelectric effect in gallium nitride micromechanical bulk acoustic filters

We report on the experimental verification of the acoustoelectric effect in gallium nitride (GaN) and present a model to describe this effect in GaN thickness-mode bulk acoustic filters. Filters are fabricated using 2.2 μm thick n-type GaN on high resistivity silicon epiwafers obtained from SOITEC. Acoustoelectric effect was observed by applying an electric field parallel to c-axis, the direction of acoustic wave propagation. Improvement in the insertion loss and out-of-band rejection was observed and Q amplifications exceeding 240% was achieved. Acoustoelectric effect makes it possible to dynamically tune the frequency response of GaN resonators and filters.