This letter reports a novel vector hydrophone based on the piezoresistive effect of resonant tunneling diode (RTD). An external pressure introduces stress in the layers of RTD and induces its current-voltage (I-V) curves change. This effect has been applied to designing new sensor. By control-hole technology, the sensor is processed integrated with GaAs/InxGa1 xAs/AlAs double barrier structures posited on its strain-sensitive region. The fabricated sensor is packaged for watertight solution, and underwater measurements are conducted in RTD's negative differential resistance (NDR) region. Directivity curve of the sensor follows "8" cosine functional form, which shows its vector sound signal detection ability, and its sensitivity reaches 184 6 dB (0dB=1V/Pa) at 1 KHz.

This paper reports a novel acoustic sensor with a frequency output based on AlAs/InxGa1−xAs/GaAs resonant tunneling diode (RTD). The RTD is incorporated in a 1um thick membrane and the fabrication technology of the membrane is based upon the selective etch of GaAs with AlAs an etch stop layer. A relaxation oscillator is obtained with the RTD biased in the negative differential resistance (NDR) region. Acoustic 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 the direct frequency output, which is linearly dependent on pressure, and the linear sensitivity can be up to 21kHz/kPa.