Piezoelectric MEMS resonators based on ultrathin epitaxial GaN heterostructures on Si

We present the first results for microelectromechanical (MEMS) resonators fabricated on epitaxial nitride semiconductors with thin buffers engineered for MEMS and NEMS applications. These results are used to assess the use of thin buffers for GaN MEMS fabrication. On a 700 nm thick AlGaN/GaN epilayer, a high tensile stress is observed to increase the resonant frequency. The electromechanical coupling efficiencies of integrated transducers are assessed and compared with previously obtained results on commercially available 2 µ m thick epilayers used for power transistor applications. A 28 nm V⁻¹ actuation efficiency is measured on the 700 nm thick structure which is slightly better than the one measured on the 2 µ m buffer. The electrical response of a gateless detector designed as a piezoresistance is obtained and a gauge factor of 60 is estimated. These results show that material issues can be unlocked to exploit the potentialities of III-nitrides for NEMS applications. (paper)