High resolution electron micrographs (HREM) of InGaN/GaN quantum wells from many research groups appear to demonstrate very indium-rich clusters on a nanometer scale and PL results suggest that the excitons in InGaN quantum wells have a localisation of about 2 nm. However, we have studied bright blue and green LEDs grown by our Thomas Swan MOCVD reactor and from elsewhere, and our HREM results using a very low intensity electron beam show no evidence for such strong indium clustering. However, nanometre-scale strain inhomogeneities are introduced into the quantum wells by radiation damage very soon after exposing the material to the electron beam. The image features caused by the radiation damage are similar to those expected to be caused by indium-rich regions so we therefore suggest that reports of indium clustering may be influenced by electron beam damage artefacts. We find that in each quantum well the lower InGaN/GaN interface is atomically smooth, but that the upper interface has atomic height steps, and the lateral scale of these steps is on a nanometer scale. Because of the strong piezoelectric effect in GaN, an atomic size step in an InGaN quantum well is sufficient to cause exciton localisation. It is suggested that this may be the mechanism, or a contributory mechanism, to the exciton localisation observed in InGaN/GaN quantum wells.

• Legal notice:
  

  Copyright (c) Pielaszek Research, all rights reserved.
  The above materials, including auxiliary resources, are subject to Publisher's copyright and the Author(s) intellectual rights. Without limiting Author(s) rights under respective Copyright Transfer Agreement, no part of the above documents may be reproduced without the express written permission of Pielaszek Research, the Publisher. Express permission from the Author(s) is required to use the above materials for academic purposes, such as lectures or scientific presentations.
  In every case, proper references including Author(s) name(s) and URL of this webpage: https://science24.com/paper/3793 must be provided.

1. Growth monitoring of nitride semiconductors at its limit
2. Quantitative Dopant Profiling in the SEM including surface states.