Spontaneous current oscillations in n-GaAs in high magnetic fields

Spontaneous regular and chaotic current oscillations have been observed in n-GaAs at 4.2 K. The dependencies of the frequency of these regular oscilla tions on the temperature and high magnetic field were investigated. A non-m onotonic dependency of the frequency on magnetic field was found for the fi rst time. The Arrhenius plot of the temperature dependence of the frequency of the regular oscillations gives an activation energy of about 0.31 meV, which is much less than the values of the ionization energies of the ground and the first excited states of the corresponding shallow impurity level i n n-GaAs. This value appears to be consistent with the activation energy fo r hopping conduction of electrons in the impurity band. (C) 1998 Elsevier S cience B.V. All rights reserved.