Designing hyperchaos and intermittency in semiconductor superlattices

TL;DR

This paper demonstrates how modifying semiconductor superlattices by inserting wider wells can induce robust hyperchaos and intermittent chaos, enhancing their potential as fast, reliable physical random number generators at room temperature.

Contribution

It introduces a novel design modification in superlattices that significantly increases excitability and chaos complexity, making chaotic behavior more resilient to noise and structural variations.

Findings

Insertion of wider wells increases superlattice excitability.

Hyperchaos and intermittent chaos are observed over extended voltage ranges.

Chaotic attractors are robust against noise and structural disorder.

Abstract

Weakly coupled semiconductor superlattices under dc voltage bias are excitable systems with many degrees of freedom that may exhibit spontaneous chaos at room temperature and act as fast physical random number generator devices. Superlattices with identical periods exhibit current self-oscillations due to the dynamics of charge dipole waves but chaotic oscillations exist on narrow voltage intervals. They disappear easily due to variation in structural growth parameters. Based on numerical simulations, we predict that inserting two identical sufficiently separated wider wells increases superlattice excitability by allowing wave nucleation at the modified wells and more complex dynamics. This system exhibits hyperchaos and varieties of intermittent chaos in extended dc voltage ranges. Unlike in ideal superlattices, our chaotic attractors are robust and resilient against noises and against controlled random disorder due to growth fluctuations.