Wurtzite quantum wires with strong spatial confinement: polarization anisotropies in single wire spectroscopy

TL;DR

This study investigates ultrathin wurtzite GaAs/AlGaAs nanowires, revealing how diameter and dielectric mismatch influence polarization anisotropies in their optical properties through combined experimental and theoretical analysis.

Contribution

It provides the first detailed polarization-resolved analysis of 1D wurtzite GaAs quantum wires, highlighting the impact of diameter and dielectric mismatch on optical anisotropies.

Findings

Large confinement energies enable resolution of multiple subband excitations.

Polarization of photoluminescence depends on wire symmetry and dielectric mismatch.

Excellent agreement between experimental data and theoretical simulations.

Abstract

We report GaAs/AlGaAs nanowires in the one-dimensional (1D) quantum limit. The ultrathin wurtzite GaAs cores between 20-40\,nm induce large confinement energies of several tens of meV, allowing us to experimentally resolve up to four well separated subband excitations in microphotoluminescence spectroscopy. Our detailed experimental and theoretical polarization-resolved study reveals a strong diameter-dependent anisotropy of these transitions: We demonstrate that the polarization of the detected photoluminescence is governed by the symmetry of the wurtzite 1D quantum wire subbands on the one hand, but also by the dielectric mismatch of the wires with the surrounding material on the other hand. The latter effect leads to a strong attenuation of perpendicularly polarized light in thin dielectric wires, making the thickness of the AlGaAs shell an important factor in the observed polarization behavior. Including the dielectric mismatch to our k.p-based simulated polarization-resolved spectra of purely wurtzite GaAs quantum wires, we find an excellent agreement between experiment and theory.