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

Abstract

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/mu Pa) 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. (C) 2015 Elsevier B.V. All rights reserved.