Tri-Electrode Sc0.3Al0.7N Piezoelectric Micromachined Ultrasound Transducers with Alternating Mode Operation for Simultaneous Multi-Resonant Functionality at Higher-Order Resonant Frequencies

This paper presents a Sc0.3Al0.7N-based tri-electrode piezoelectric micromachined ultrasound transducer (PMUT) with an annular ring and a circular top electrode, along with a single circular bottom electrode. A novel method of device operation using different electrode pairs as terminal and ground interfaces for various resonant modes is explored, with the intent of achieving improved multi-frequency operation with a single device design. The receiving and transmitting performance of the device is experimentally examined and the proposed tri-electrode PMUT shows improved transmission and receiving performance at high order modes from 2nd to 4th order by utilizing the annular top electrode as the terminal. In addition, by utilizing the circular top electrode as the terminal, the same device can operate without compromising performance at the 1st order resonant frequency compared to a traditional device, promising multi-resonant performance if the operation modes are alternated.