Electron dynamics in intentionally disordered semiconductor superlattices

TL;DR

This study investigates how intentional short-range correlated disorder in semiconductor superlattices affects electron dynamics, revealing conditions for ballistic transport and potential for nanotechnological filtering devices.

Contribution

It demonstrates that correlated disorder can induce extended states with ballistic transport, contrasting with usual exponential growth in transmission time in disordered superlattices.

Findings

Extended states exhibit ballistic transport close to ideal superlattices.

Correlated disorder causes significant filtering of incident signals.

Control of output band is possible with an applied dc electric field.

Abstract

We study the dynamical behavior of disordered quantum-well-based semiconductor superlattices where the disorder is intentional and short-range correlated. We show that, whereas the transmission time of a particle grows exponentially with the number of wells in an usual disordered superlattice for any value of the incident particle energy, for specific values of the incident energy this time increases linearly when correlated disorder is included. As expected, those values of the energy coincide with a narrow subband of extended states predicted by the static calculations of Dom\'{\i}nguez-Adame {\em et al.} [Phys. Rev. B {\bf 51}, 14 ,359 (1994)]; such states are seen in our dynamical results to exhibit a ballistic regime, very close to the WKB approximation of a perfect superlattice. Fourier transform of the output signal for an incident Gaussian wave packet reveals a dramatic filtering of the original signal, which makes us confident that devices based on this property may be designed and used for nanotechnological applications. This is more so in view of the possibility of controllingthe outp ut band using a dc electric field, which we also discuss. In the conclusion we summarize our results and present an outlook for future developments arising from this work.