Piezoelectric actuated epitaxially grown AlGaN/GaN-resonators
In this work we present a novel concept of piezoelectrically actuated MEMS resonators based on AlGaN/GaNheterostructures. The 2DEG, which is confined at the AlGaN/GaN interface, serves as back electrode for piezoelectric actuation and read-out. Using the inverse piezoelectric effect longitudinal in-plane mechanical oscillations could be exited by applying a RF signal to the drive contacts. Through the charges, which were generated by the direct piezoelectric effect a sensor signal could be detected at the sense contacts of the integrated resonator structure. This enables the measurement of longitudinal resonant frequencies up to the 4th mode with values from 3 to 63 MHz. The investigations were carried out in various ambient pressure conditions, which exemplarily demonstrate the sensitivity of the quality factor to environmental parameters. Thereby the AlGaN/GaN resonators showed the highest sensitivity in the region of viscous damping, which leads to the possibility of sensor applications concerning the property determination of gaseous or even liquid surrounding conditions.