Design and Characterization of a Sc20%Al1-20%N-Based PMUTs Array for an Underwater Communication System

The exploration of the ocean depends heavily on effective underwater communication. There is a significant promise in this study and development of high-performance sensors tailored specifically for underwater communications. This work presents a high-performance sensor utilizing a scandium-doped aluminum nitride (Sc20%Al1%–20%N) piezoelectric micromachined ultrasonic transducers (PMUTs) array, specifically designed for underwater communications applications. The PMUTs array, which consists of
${7} \times $
sensing cells with a feature size of
$500~\mu $
m, is being developed on a silicon-on-insulator (SOI) piezoelectric platform. The PMUTs array is bonded with a preamplification circuit, and packaged together with a polydimethylsiloxane (PDMS) layer to provide good acoustic impedance matching to water. The packaged PMUTs array is fully characterized using an industry-standard calibration instrument. The experimental results show that the PMUTs array exhibits electromechanical coupling factors of 2.24% in air and 3.56% in water, respectively. The PMUTs array is omnidirectional after packaging with a minimum deviation of ±0.5 dB at 1 kHz. The reported PMUTs array achieves a receiving sensitivity of −172 dB (re: 1 V/
$\mu $
Pa) with a 40-dB gain. Notably, the acceleration sensitivity is approximately 21 dB lower than the acoustic pressure sensitivity. It achieves lower bit error rates (BERs) compared to commercial transducers, thereby enhancing overall communication reliability and performance. The measured results show that the design of the PMUTs array for underwater communications sensor application compares favorably with advanced commercially available transducers and a good prospect in commercial application.