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

The work of the last two decades on RTDs has been dominated by the needs of semiconductor heterostructure devices for high frequency operation and high speed applications. The fast transit time of the quantum effect involved in the conduction mechanism and the exhibited negative differential resistance have motivated these extensive efforts. The development of the band-gap engineering has opened the possibility of using different material systems in order to extend RTD operation frequencies to the THz-region. Oscillations of up to 712 GHz have been reported and several applications of RTDs for multivalued logic have been proposed [1-3]. However the RTD currentvoltage characteristics show, as explained below, a special uniaxial stress dependence, mainly in the negative differential resistance region. This dependence is used in this work to modulate the frequency of a relaxation oscillator which includes an Al0.6Ga0.4As/GaAs RTD.