Self-sustained Current Oscillations Research Articles

Simulation of negative resistance and current instabilities in a p-i-n Si diode

Current instabilities in a p-i-n Si diode heavily doped with gold impurities are investigated numerically. In order to clarify the explicit effect of the space charge of impurities on the current instabilities, we re-examine numerically the steady-state solutions for this particular diode without the quasineutrality assumption. The linearized stability analysis shows that the spontaneous self-sustained current oscillations can occur in the low-injection regime, where the DC resistance remains positive.

Regular and chaotic current oscillations in n-type GaAs in transverse and longitudinal magnetic fields.

Self-sustained current oscillations due to impurity breakdown in n-type GaAs epitaxial layers are reported for various magnetic-field strengths and orientations of the field with respect to the direction of current. In all cases relaxation oscillations at the onset of breakdown and formation of a current filament in the postbreakdown regime are observed. A magnetic field normal to the epitaxial layer destabilizes the filament and causes multifrequency oscillations and chaotic fluctuations. On the other hand, if the magnetic field lies in the plane of the layer the filamentary current flow is stable up to field strengths of 2 T.

Nonlinear energy relaxation oscillations and chaotic dynamics of hot carriers

It is shown that recently observed complex chaotic behavior associated with low temperature impurity breakdown can be understood by introducing the mean energy per carrier E as an additional dynamic variable besides the carrier densities. A set of coupled nonlinear evolution equations for the carrier density and mean energy is derived by a moment expansion of the Boltzmann equation including, in particular, impact ionization. This process leads to a novel, strongly nonlinear relaxation term in the dynamic energy balance equation. The simplest, spatially homogeneous version of the model yields hysteretic or non-hysteretic static current-voltage characteristics, and spontaneous self-sustained current oscillations. It can also be used to explain the coupling of the oscillations in two spatially separated hot carrier subsystems via energy exchange.