High frequency dynamic bending response of piezoresistive GaN microcantilevers

Static and dynamic ac responses of piezoresistive GaN microcantilevers, with integrated AlGaN/GaN heterostructure field effect transistors as highly sensitive deflection transducers, have been investigated. Very high gauge factor exceeding 3500 was exhibited by the microcantilevers, with quality factor determined from electronically transduced ac response exceeding 200 in air and 4500 at low pressure. The gauge factor reduced at resonance frequency of the cantilevers, possibly due to reduced charge exchange with surface donor and trap states. Ultrasonic waves generated in air by a piezochip, and in the Si substrate through photoacoustic effect, could be detected by the cantilevers with high sensitivity. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4772489]