Impact of Biasing Conditions on Displacement Transduction by III-Nitride Microcantilevers

The impact of biasing conditions on the sensitivity of an AlGaN/GaN heterojunction field-effect transistor deflection transducer, fabricated at the base of a GaN microcantilever, has been investigated. The gauge factor is found to increase with negative gate bias, reaching 3200 at 3.1 V, which is at least an order of magnitude higher than Si piezoresistors. Ultrahigh ac deflection responsivity has also been observed, which reached a maximum value of 140 μV/nm at a gate bias of 2.3 V, consuming only 51 μW of power.