A GaAs pressure sensor with frequency output based on resonant tunneling diodes

We present a novel bulk semiconductor pressure sensor based on an Al_xGa_1-xAs/GaAs resonant tunneling diode (RTD) with a frequency output. 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. Frequency measurements have been performed on (001)-oriented RTD´s with [110]-compressive uniaxial pressure. Sensitivities of up to 0.8 kHz/MPa at 113 kHz have been measured. The main feature of this sensor type is the direct frequency output obtained by using only a maximum of three components including the RTD. Using a simplified differential equation of the oscillator circuit, the pressure-dependent effects of the RTD current-voltage characteristics on the sensor output have been investigated