Unveiling the 3D Morphology of Epitaxial GaAs/AlGaAs Quantum Dots

TL;DR

This paper provides a detailed 3D structural analysis of GaAs/AlGaAs quantum dots grown by DENI, revealing their morphology and element distribution to aid in optimizing their optoelectronic properties.

Contribution

It introduces a comprehensive 3D morphological model of GaAs/AlGaAs QDs using advanced microscopy and chemical etching techniques, filling a knowledge gap in their structural understanding.

Findings

Inverted conical nanohole structure with Al-rich sidewalls

Asymmetrical element distribution within QDs

Defect-free interfaces confirmed by STEM

Abstract

Strain-free GaAs/AlGaAs semiconductor quantum dots (QDs) grown by droplet etching and nanohole infilling (DENI) are highly promising candidates for the on-demand generation of indistinguishable and entangled photon sources. The spectroscopic fingerprint and quantum optical properties of QDs are significantly influenced by their morphology. The effects of nanohole geometry and infilled material on the exciton binding energies and fine structure splitting are well understood. However, a comprehensive understanding of GaAs/AlGaAs QD morphology remains elusive. To address this, we employ high-resolution scanning transmission electron microscopy (STEM) and reverse engineering through selective chemical etching and atomic force microscopy (AFM). Cross-sectional STEM of uncapped QDs reveals an inverted conical nanohole with Al-rich sidewalls and defect-free interfaces. Subsequent selective chemical etching and AFM measurements further reveal asymmetries in element distribution. This study enhances the understanding of DENI QD morphology and provides a fundamental three-dimensional structural model for simulating and optimizing their optoelectronic properties.