Nonlinear charge transport and excitable phenomena in semiconductor superlattices

L. Bonilla, M. Carretero, E. Mompó

Entropy Vol. 26, nº. 8, pp. 672-1 - 672-23

Summary:

Semiconductor superlattices are periodic nanostructures consisting of epitaxially grown quantum wells and barriers. For thick barriers, the quantum wells are weakly coupled and the main transport mechanism is a sequential resonant tunneling of electrons between wells. We review quantum transport in these materials, and the rate equations for electron densities, currents, and the self-consistent electric potential or field. Depending on superlattice configuration, doping density, temperature, voltage bias, and other parameters, superlattices behave as excitable systems, and can respond to abrupt dc bias changes by large transients involving charge density waves before arriving at a stable stationary state. For other parameters, the superlattices may have self-sustained oscillations of the current through them. These oscillations are due to repeated triggering and recycling of charge density waves, and can be periodic in time, quasiperiodic, and chaotic. Modifying the superlattice configuration, it is possible to attain robust chaos due to wave dynamics. External noise of appropriate strength can generate time-periodic current oscillations when the superlattice is in a stable stationary state without noise, which is called the coherence resonance. In turn, these oscillations can resonate with a periodic signal in the presence of sufficient noise, thereby displaying a stochastic resonance. These properties can be exploited to design and build many devices. Here, we describe detectors of weak signals by using coherence and stochastic resonance and fast generators of true random sequences useful for safe communications and storage.

Spanish layman's summary:

Las superredes semiconductoras son nanoestructuras con pozos y barreras cuánticas. El transporte electrónico ocurre por túnel resonante, generando comportamientos excitables, oscilaciones y caos. Esto permite crear detectores de señales débiles y generadores de secuencias aleatorias seguras.

English layman's summary:

Semiconductor superlattices are nanostructures with quantum wells and barriers. Electron transport occurs via resonant tunneling, leading to excitable behavior, oscillations, and chaos. These devices can be used as weak signal detectors and random sequence generators for secure communications.

Keywords: semiconductor superlattices; resonant quantum tunneling; quantum transport; excitable media; coherence resonance; stochastic resonance; self-sustained oscillations; chaos

JCR Impact Factor and WoS quartile: 2,100 - Q2 (2023)

DOI reference: https://doi.org/10.3390/e26080672

Published on paper: August 2024.

Published on-line: August 2024.

Citation:
L. Bonilla, M. Carretero, E. Mompó, Nonlinear charge transport and excitable phenomena in semiconductor superlattices. Entropy. Vol. 26, nº. 8, pp. 672-1 - 672-23, August 2024. [Online: August 2024]