# Bismuth-surfactant-induced growth and structure of InAs/GaAs(110) quantum dots

## TL;DR

This study demonstrates how bismuth surfactant influences the growth mode, structure, and strain relaxation of InAs quantum dots on GaAs(110), enabling controlled quantum dot formation through molecular beam epitaxy.

## Contribution

It reveals the role of Bi surfactant in inducing and controlling 3D InAs quantum dot growth on GaAs(110), which normally does not support such formation.

## Key findings

- Bi flux changes InAs growth from 2D to 3D islands.
- Larger islands are plastically relaxed, small ones are coherent.
- Strain relaxation occurs via specific dislocation types along different directions.

## Abstract

We explore the Bi-surfactant-directed self-assembly and structure of InAs quantum dots grown on GaAs(110) by molecular beam epitaxy. The addition of a Bi flux during InAs deposition changes the InAs growth mode from two-dimensional (2D) Frank-van der Merwe to Stranski-Krastanov, resulting in the formation of three-dimensional (3D) InAs islands on the surface. Furthermore, exposing static InAs 2D layers to Bi induces a rearrangement of the strained layer into 3D islands. We explore the effect of varying the InAs thickness and Bi flux for these two growth approaches, observing a critical thickness for 3D island formation in both cases. Characterization of (110) InAs quantum dots with high-resolution transmission electron microscopy reveals that larger islands grown by the Stranski-Krastanov mode are plastically relaxed, while small islands grown by the on-demand approach are coherent. Strain relaxation along the [1-10] direction is achieved by 90 degree pure-edge dislocations with dislocation lines running along [001]. In contrast, strain relief along [001] is by 60 degree misfit dislocations. This behaviour is consistent with observations of planar (In,Ga)As/GaAs(110) layers. These results illustrate how surfactant Bi can provoke and control quantum dot formation where it normally does not occur.

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Source: https://tomesphere.com/paper/1905.05303