Theoretical Analysis and Verification on ScAlN-Based Piezoelectric Micromachined Ultrasonic Transducers With DC Bias

Applying a DC bias can effectively tune the performance of a piezoelectric ultrasonic micromachined transducer (PMUT) to meet the requirements in multiple application scenarios. However, the effect of DC bias on various parameters of PMUT has not been systematically analyzed and verified. In this work, a theoretical model of scandium-doped aluminum nitride (ScAlN) based PMUT under different DC biases is obtained by extracting new effective coefficients and coupling the DC bias into the vibration functions. The measurement results show that the resonant frequency, center displacement, −3-dB bandwidth, and electromechanical coupling coefficient of ScAlN-based PMUT all change linearly when the DC bias is swept from −90-V to 90-V. Moreover, the sensitivity of resonant frequency is 185-Hz/V, and the effective frequency range is 32.81-kHz. The electromechanical coupling coefficient increased more than 14.18 % at 40-V compared to −40-V. The theoretical model is verified with the experimental measurement and indicates that the performance of ScAlN-based PMUT is tunable through DC bias, which has considerable application potential in application scenarios such as data communication, photoacoustic imaging, pulse-echo positioning, and phased array. [2023-0111]