# Design and Development of Sc0.2Al0.8N-Based Dual-Piezoelectric-Layer MEMS Hydrophone

## TL;DR

A new MEMS hydrophone with a dual-piezoelectric-layer design improves sensitivity and frequency range for underwater sound detection.

## Contribution

The dual-piezoelectric-layer design using Sc0.2Al0.8N expands frequency response and enhances sensitivity in MEMS hydrophones.

## Key findings

- The device achieves an average sound pressure sensitivity of −162 dB across 20 Hz–50 KHz.
- It has an equivalent noise density of 47 dB with 99% linearity.

## Abstract

An innovative design for a dual-piezoelectric-layer MEMS hydrophone based on a composite film of scandium-doped aluminum nitride (Sc0.2Al0.8N) is presented. By designing the dual piezoelectric layer, the frequency response range has been expanded and the sensitivity of the device has been significantly enhanced. Meanwhile, doping with scandium can significantly increase the piezoelectric coefficient, enhancing the sensitivity. According to the standard underwater acoustic calibration test, the device exhibits an average sound pressure sensitivity of −162 dB (re: 1 V/μPa) across the 20 Hz–50 KHz frequency band and equivalent noise density of 47 dB (re: 1 μPa/√Hz) with a linearity of 99%. The experimental results show that the comprehensive performance of the dual-piezoelectric-layer hydrophone provides a new solution for underwater sensing and detection, and opens up a new path for the performance optimization of passive sonar systems.