Carrier density dependence of transitions between chaotic and periodic photocurrent oscillations in undoped GaAs/AlAs superlattices

Abstract

The carrier density dependence of self-sustained photocurrent oscillations originating from unstable electric-field domains has been investigated in an undoped, weakly-coupled GaAs/AlAs superlattice. The frequency spectra of the oscillations reveal transitions between regions of periodic and chaotic oscillations as well as static regions as a function of bias. The chaotic oscillations appear in regions with a very large negative differential conductance. As the excitation intensity is increased further, the voltage regimes exhibiting oscillations become narrower, while the static windows become wider. This observation indicates that the electric-field domain distribution is changing with increasing carrier density from an unstable to a static distribution.