A Study on PVD PZT and Sc _0.2 Al _0.8 N PMUTS in Series and Parallel Connection for Optimizing Acoustic Performance

This work presents an experimental comparative analysis of acoustic performance for series and parallel connected piezoelectric micromachined ultrasonic transducers (PMUTs) designed and fabricated in physical vapor deposition (PVD) lead zirconate titanate (PZT) and 20% scandium (Sc)-doped aluminum nitride (AlN). The aim of this research is to provide insights for optimizing PMUT array design by the choice of electrical connections in relation to material selection. In parallel connection, the current generated by PMUTs is merged and the output impedance of the device becomes lower than the output impedance of single PMUT. In series connection, the output impedance and the voltage output of PMUTs increase with the number of series connections. From the experimental results of a PMUT array with 16-membranes (each membrane represents single PMUT element), series connection shows better receive (RX) sensitivity for PZT with 4.6 mV/ Pa as compared to 2.05 mV/Pa for parallel connection, while ScAlN fared better in parallel connection with 46 mV/Pa as compared to 36 mV/Pa for series connection which are closely matched to simulated values.