Thermally-driven formation of Ge quantum dots on self-catalysed thin GaAs nanowires

TL;DR

This paper demonstrates a thermally-driven method to form Ge quantum dots on self-catalyzed GaAs nanowires, overcoming curvature and facet growth challenges, enabling new optoelectronic device possibilities.

Contribution

It introduces a novel high-temperature annealing process to induce 3D Ge quantum dot formation on nanowires without surfactants or surface treatments.

Findings

Ge quantum dots can be formed on {110} facets of GaAs nanowires.

The 2D-3D transition is driven by energy minimization during annealing.

Method is applicable regardless of nanowire diameter or elastic strain constraints.

Abstract

Embedding quantum dots (QDs) on nanowire (NW) sidewalls allows the integration of multi-layers of QDs into the active region of radial p-i-n junctions to greatly enhance light emission/absorption. However, the surface curvature makes the growth much more challenging compared with growths on thin-films, particularly on NWs with small diameters ({\O} <100 nm). Moreover, the {110} sidewall facets of self-catalyzed NWs favor two-dimensional growth (2D), with the realization of three-dimensional (3D) Stranski-Krastanow growth becoming extremely challenging. Here, we demonstrate thermally-driven formation of Ge dots on the {110} sidewalls facets of thin self-catalyzed NWs without using any surfactant or surface treatment. The 2D-3D transition of the pseudomorphic Ge layer grown on GaAs NWs is driven by energy minimization under high-temperature annealing. This method opens a new avenue to integrate QDs on NWs without any restriction on NW diameter or elastic strain, which can allow the formation of QDs in a wider range of materials systems where the growth of islands by traditional mechanisms is not possible, with benefits for novel NWQD-based optoelectronic devices.