# Noise-enhanced chaos in a weakly coupled GaAs/(Al,Ga)As superlattice

## TL;DR

This paper demonstrates that external noise can induce and enhance chaotic current oscillations in a GaAs/AlGaAs superlattice at room temperature, supported by experiments and simulations based on a nonlinear tunneling model.

## Contribution

It provides the first detailed experimental and simulation evidence of noise-induced chaos in a weakly coupled superlattice at room temperature.

## Key findings

- Noise increases the range of bias voltages with chaotic oscillations.
- Chaotic spikes are triggered by small fluctuations at domain boundaries.
- Simulations qualitatively match experimental observations.

## Abstract

Noise-enhanced chaos in a doped, weakly coupled GaAs/Al_{0.45}Ga_{0.55}As superlattice has been observed at room temperature in experiments as well as in the results of the simulation of nonlinear transport based on a discrete tunneling model. When external noise is added, both the measured and simulated current-versus-time traces contain irregularly spaced spikes for particular applied voltages, which separate a regime of periodic current oscillations from a region of no current oscillations at all. In the voltage region without current oscillations, the electric field profile consist of a low-field domain near the emitter contact separated by a domain wall consisting of a charge accumulation layer from a high-field regime closer to the collector contact. With increasing noise amplitude, spontaneous chaotic current oscillations appear over a wider bias voltage range. For these bias voltages, the domain boundary between the two electric-field domains becomes unstable, and very small current or voltage fluctuations can trigger the domain boundary to move toward the collector and induce chaotic current spikes. The experimentally observed features are qualitatively very well reproduced by the simulations. Increased noise can consequently enhance chaotic current oscillations in semiconductor superlattices.