Piezoelectric micromachined ultrasonic transducers with increased coupling coefficient via series transduction

This work demonstrates a new electrode configuration for piezoelectric micromachined ultrasonic transducers (PMUTs) with increased electromechanical coupling coefficient (k
_t
²
). The electrodes, a center electrode surrounded by a ring electrode, are identical to those used in differential PMUTs. Unlike a differential PMUT, where the two top electrodes (TEs) are referenced to a common ground electrode, here only the two TEs are used, effectively putting the two piezoelectric transducers in series. The benefit of series readout is that the transducer's electrical capacitance is halved, doubling the receive sensitivity and electromechanical coupling coefficient k
_t
²
.