Resonant Piezoelectric ALGaN/GaN MEMS Sensors in Longitudinal Mode Operation

Free-standing piezoelectric AlGaN/GaN beam resonators have been prepared on silicon substrates using a semiconductor fabrication process. To realize the back electrode for the piezoelectric active layer, the two-dimensional electron gas at the interface of the III/V heterostructure was employed. Longitudinal acoustic resonances have been excited and detected electrically. The fundamental and higher order vibration modes were analyzed in the frequency domain. The dependences of the measured resonant frequencies between 3.8 and 63.0 MHz are related to geometrical and material parameters. The sensitivity of the resonant response to environmental parameters is demonstrated exemplarily by investigating its dependence on ambient pressure.