A Novel AlN/Sc0.2Al0.8N-Based Piezoelectric Composite Thin-Film-Enabled Bioinspired Honeycomb MEMS Hydrophone

An innovative design of a hydrophone based on a piezoelectric composite film of AlN/Sc0.2Al0.8N is presented. By designing a non-uniform composite sensitive layer, the dielectric loss and defect density are significantly reduced, while the high-voltage electrical characteristics of scandium-doped aluminum nitride are retained. X-ray diffraction analysis shows that the sensitive films have excellent crystal quality (FWHM is 0.34°). According to the standard underwater acoustic calibration test, the device exhibits full directivity with a minimum deviation of ±0.5 dB at 1 kHz frequency, sound pressure sensitivity of −162.9 dB (re: 1 V/μPa) and equivalent noise density of 46.1 dB (re: 1 μPa/√Hz). The experimental results show that the comprehensive performance of the piezoelectric heterostructure hydrophone meets the standard of commercial high-end hydrophones while maintaining mechanical stability, and provides a new solution for underwater acoustic sensing.