Beyond transmission electron microscopy imaging: Atom probe tomography reveals chemical inhomogeneity at stacking fault interfaces in InGaN/GaN light-emitting diodes

Abstract

In this study, we present an atom probe tomography investigation of zincblende InGaN-based multi-quantum well light-emitting diode (LED) structures with a specific focus on the influence of stacking faults within the system. We demonstrate that the visualisation of stacking faults in atom probe reconstructions is possible due to previously documented sensitivities of measured composition in III-V materials to local variations in electric field during the experiment. Meanwhile, we quantify the composition of indium (In) in the InGaN quantum wells and establish that elongated regions exist, parallel to ridges on the sample surface, in which the indium content is increased. We discuss this observation in the context of previous scanning transmission electron microscopy (STEM) data which suggested that such In rich regions are associated with stacking faults. Our experiments not only showcase the feasibility of stacking fault characterization in InGaN-based multi-quantum well LEDs through atom probe tomography (APT) but also offer a practical pathway towards three-dimensional imaging and compositional analysis of stacking faults at the atomic scale.