Resonant and negative resistive currents between isolated GaAs device structures

As part of an investigation into low frequency dispersions in GaAs MESFETs, extensive measurements have been made of the impedance between adjacent isolated n-type mesa structures. It was possible to observe a transition from inductive to capacitive behaviour as frequency was increased. The resonance at room temperature was between 100 Hz and a few kHz. The same measurements also showed that there were ranges of frequency where the real part of the impedance was negative. Mathematical modelling has been carried out in order to give support to the models that are proposed. Inductive behaviour can be explained by the passage of charge through a single trap. It is shown that a region of negative resistance can result when charge passing between the mesas suffers multiple trapping and passes successively through at least two traps. Comparisons are be made between experimental data and simulations based on these mechanisms.