A novel cantilever acoustic sensor with frequency output based on resonant tunneling diodes

This paper reports a novel GaAs cantilever acoustic sensor based on AlAs/In
_x
Ga
_1-x
As/GaAs resonant tunneling diode (RTD) with a frequency output. The RTD is incorporated in a 10 mum thick cantilever diaphragm and the fabrication technology of the cantilever diaphragm is based upon the micromachined control holes technology. A relaxation oscillator is obtained with the RTD biased in the negative differential resistance (NDR) region. Pressure applied to the RTD changes the frequency of oscillation due to the shift in current-voltage characteristics. The main feature of this sensor type is the direct frequency output and the sensitivity can be up to 102kHz/kPa