Detection of Acoustic Waves with a PI-DMOS Transducer

A new type of fast and sensitive pressure transducer, the piezoelectric DMOS transducer (PI-DMOS), is described. The device is basically a double-diffused MOS transistor (DMOST) with a piezoelectric layer of ZnO incorporated as part of the gate insulator. Bulk acoustic waves at frequencies ranging from 1 MHz to 30 MHz have been detected with nearly constant strain sensitivity. The PI-DMOS transistor has also been used to sense surface acoustic waves at 20 and 28 MHz. The limiting frequency of device operation can extend to the GHz range. Measured gauge factors for the PI-DMOS transistor at low frequencies were in excess of 105. Response time to a shock input in less than 400 ns was observed. The strain-sensitive area of the PI-DMOS transducer corresponds to the DMOST channel area and is roughly 800 (µm)2.