Intentionally disordered superlattices with high dc conductance

TL;DR

This paper demonstrates that intentional short-range correlated disorder in semiconductor superlattices can create extended electronic states, significantly enhancing dc conductance even with imperfections, suggesting new device applications.

Contribution

It reveals that structural correlations in disordered superlattices can inhibit localization, leading to high conductance, a novel insight for designing electronic materials.

Findings

Existence of a band of extended states in correlated disordered superlattices

Enhanced dc conductance when Fermi level matches the extended state band

Robustness of extended states despite interface roughness

Abstract

We study disordered quantum-well-based semiconductor superlattices where the disorder is intentional and short-range correlated. Such systems consist of quantum-wells of two different thicknesses randomly distributed along the growth direction, with the additional constraint that wells of one kind always appears in pairs. Imperfections due to interface roughness are considered by allowing the quantum-well thicknesses to fluctuate around their {\em ideal} values. As particular examples, we consider wide-gap (GaAs-Ga$_{1-x}$Al$_{x}$As) and narrow-gap (InAs-GaSb) superlattices. We show the existence of a band of extended states in perfect correlated disordered superlattices, giving rise to a strong enhancement of their finite-temperature dc conductance as compared to usual random ones whenever the Fermi level matches this band. This feature is seen to survive even if interface roughness is taken into account. Our predictions can be used to demonstrate experimentally that structural correlations inhibit the localization effects of disorder, even in the presence of imperfections. This effect might be the basis of new, filter-like or other specific-purpose electronic devices.