A Photonic Atom Probe Analysis of the Effect of Extended and Point Defects on the Luminescence of InGaN/GaN Quantum Dots

TL;DR

This study uses correlative microscopy and atom probe tomography to investigate how extended and point defects affect the luminescence of InGaN/GaN quantum dots, revealing defect-related trapping and strain relaxation effects.

Contribution

It provides new insights into defect-induced luminescence behavior in quantum dots using combined microscopy and atom probe techniques.

Findings

Luminescence intensity increases near the surface despite higher defect density.

Quantum dot layers closer to the substrate act as traps for non-radiative point defects.

Single quantum dot emission shows spectral shifts indicating strain relaxation.

Abstract

We report a correlative microscopy study of a sample containing three stacks of InGaN/GaN quantum dots (QDs) grown at different substrate temperature, each stack consisting of 3 layers of QDs. Decreasing the substrate temperature along the growth axis leads to the proliferation of structural defects. However, the luminescence intensity increases towards the surface, in spite of the higher density of threading dislocations, revealing that the QD layers closer to the substrate behave as traps for non-radiative point defects. During atom probe tomography experiments combined with in-situ micro-photoluminescence, it was possible to isolate the optical emission of a single QD located in the topmost QD stack, closer to the sample surface. The single QD emission line displayed a spectral shift during the experiment confirming the relaxation of elastic strain due to material evaporation during atom probe tomography.