A new transduction mechanism for hydrophones employing piezoelectricity and a field-effect transistor

In contrast to the induced charge or voltage in conventional piezoelectric hydrophones, changes in the bound surface charge density and the corresponding changes in the electric field from a piezoelectric body do not depend on the size of the piezoelectric material. In this paper, we describe a new transduction mechanism, the piezoelectric gate on a field-effect transistor (PiGoFET), for applications in hydrophones. We describe a theoretical model of the PiGoFET, which shows that high sensitivity can be achieved with a small hydrophone due to the size independence of the PiGoFET transduction mechanism. A PiGoFET hydrophone was designed, fabricated, and characterized. The measured sensitivity was −175.5 ± 1 dB (Ref. V/μPa) at frequencies in the range 50-500 Hz. The measured frequency response was in agreement with the simulated data to within 2 dB. These results demonstrate potential applications in hydrophones, especially for wide-band and low-frequency applications, as well as in micro-hydrophones.