Contact-related current oscilations in semi-insulating GaAs

Abstract

Spontaneous current oscillations in semi-insulating GaAs were investigated at room temperature. The sample used had three contacts of different shapes. For each pair of contacts the measurements were done for both directions of the current flow. The current-voltage characteristics showed an ohmic part which was followed by a sublinear part. Depending on the chosen contacts and the polarization, the onset of oscillations was found in the first or in the second part. One or few frequencies were visible at the threshold. In each case the activation energy of the conduction electron concentration, measured at the onset of oscillations, was equal to 0.54 eV. The activation energies of the observed frequencies were between 0.56 and 1.30 eV. Possible mechanisms for the appearance of the oscillations are discussed.