An acoustic sensor with the resonant tunnelling effects of GaAs/AlAs/InGaAs hetero structures

This paper reports an acoustic sensor based on AlAs/InGaAs/GaAs resonant tunnelling diode (RTD). The RTD is incorporated in a 10 mu m thick cantilever using inductivity coupled plasma (ICP) technology and the fabrication of the cantilever diaphragm is based upon micro machined control holes technology by ICP too. Pressure applied to RTD changes its current-voltage characteristics, which can be used on sensor design. Comparing with sensors using Si technology, this type of sensor has excellence features, such as indecisive of temperature effects, high sensitivity, half-digital outputs and so on. Because of the restriction of RTD's fabricated technology, the negative differential region (NDR) of RTD hasn't been used in this batch, which induces the sensor's sensitivity is not very high. Elementary measurements show the acoustic sensor has a good frequency response in 500 HZ region between 1.3 KHZ and 1.8KHz, and its sensitivity up to 0.1 mu v/Pa with frequency f=1.3KHL.