Quantum dot self-assembly driven by a surfactant-induced morphological instability

TL;DR

This paper demonstrates that surfactants like bismuth can induce the self-assembly of quantum dots from 2D layers in strained heteroepitaxy, enabling controlled quantum dot formation through surface energy modification.

Contribution

It introduces a method to induce quantum dot self-assembly using surfactants, specifically showing how Bi triggers 3D island formation in InAs/GaAs growth.

Findings

Bi reduces the energetic barrier for 3D island formation.

Surfactant presence switches growth mode from 2D to 3D.

Quantum dots formed are optically active.

Abstract

In strained heteroepitaxy, two-dimensional (2D) layers can exhibit a critical thickness at which three-dimensional (3D) islands self-assemble, relieving misfit strain at the cost of an increased surface area. Here we show that such a morphological phase transition can be induced on-demand using surfactants. We explore Bi as a surfactant in the growth of InAs on GaAs(110), and find that the presence of surface Bi induces Stranski-Krastanov growth of 3D islands, while growth without Bi always favors 2D layer formation. Exposing a static two monolayer thick InAs layer to Bi rapidly transforms the layer into 3D islands. Density functional theory calculations reveal that Bi reduces the energetic cost of 3D island formation by modifying surface energies. These 3D nanostructures behave as optically active quantum dots. This work illustrates how surfactants can enable quantum dot self-assembly where it otherwise would not occur.