We study the origin of bimodal emission in AlGaN/AlN QD superlattices displaying high internal quantum efficiency (around 50%) in the 230-300 nm spectral range. The secondary emission at longer wavelengths is linked to the presence of cone-like defects starting at the first AlN buffer/superlattice interface and propagating vertically. These defects are associated with a dislocation that produces strong shear strain, which favors the formation of 30{\deg} faceted pits. The cone-like structures present Ga enrichment at the boundary facets and larger QDs within the defect. The bimodality is attributed to the differing dot size/composition within the defects and at the defect boundaries, which is confirmed by the correlation of microscopy results and Schr\"odinger-Poisson calculations.
@article{arxiv.2310.04201,
title = {Effect of extended defects on AlGaN QDs for electron-pumped UV-emitters},
author = {Jesus Cañas and Névine Rochat and Adeline Grenier and Audrey Jannaud and Zineb Saghi and Jean-Luc Rouviere and Edith Bellet-Amalric and Anjali Harikumar and Catherine Bougerol and Lorenzo Rigutti and Eva Monroy},
journal= {arXiv preprint arXiv:2310.04201},
year = {2024}
}