Local disorder and optical properties in V-shaped quantum wires : towards one-dimensional exciton systems

TL;DR

This study investigates exciton localization in V-shaped GaAs/GaAlAs quantum wires, revealing how improved growth techniques lead to increased delocalization and the formation of one-dimensional exciton states, despite residual disorder.

Contribution

It demonstrates the evolution of exciton localization from quantum boxes to 1D continuum states as growth techniques improve in V-shaped quantum wires.

Findings

Localization length increased with better growth techniques

Delocalized excitons form 1D states in micron-sized islands

Residual disorder causes electron-hole separation due to piezo-electric fields

Abstract

The exciton localization is studied in GaAs/GaAlAs V-shaped quantum wires (QWRs) by high spatial resolution spectroscopy. Scanning optical imaging of different generations of samples shows that the localization length has been enhanced as the growth techniques were improved. In the best samples, excitons are delocalized in islands of length of the order of 1 micron, and form a continuum of 1D states in each of them, as evidenced by the sqrt(T) dependence of the radiative lifetime. On the opposite, in the previous generation of QWRs, the localization length is typically 50 nm and the QWR behaves as a collection of quantum boxes. These localization properties are compared to structural properties and related to the progresses of the growth techniques. The presence of residual disorder is evidenced in the best samples and explained by the separation of electrons and holes due to the large in-built piezo-electric field present in the structure.