Circuit-limited oscillations at the onset of impurity breakdown in ultrapure p-Ge with an S-shaped current-field characteristic

Ultrapure p-Ge with doping concentration as low as ∼1011 cm−3 is considered to investigate self-pulsating oscillations at the onset of impurity breakdown with respect to an S-shaped current-field characteristic. The associated nonlinear dynamics is computed within the two-impurity-level model with more convincing parameterization. The system undergoes a single Hopf bifurcation in the presence of a sufficiently large circuitry capacitance. As the operating point is controlled towards the breakdown threshold, no further bifurcations but a changeover of the periodic oscillation occurs from being sinusoidal to pulsating. Our approach also obtains agreeable results for n-GaAs with typically higher doping.