ABSTRACT
Atomic force microscopy was used to characterise InGaN-based structures grown by metal-organic vapour phase epitaxy at temperatures between 760 and 860°C. The samples studied included thick InGaN layers, and InGaN/GaN multiple quantum wells on both conventional GaN buffer layers and a GaN template layer produced by epitaxial lateral overgrowth. An important role played by threading dislocations (TD) is the nucleation of pits in InGaN-based structures grown on GaN buffer or template layers. Line defects in GaN, including TD and nanopipes, have been investigated intensively because of their impact on the performance of devices. To identify and quantify line defects, transmission electron microscopy (TEM) is the most powerful and versatile technique, although it traditionally depends on lengthy sample preparation processes. V-pits in InGaN/GaN multiple quantum wells have been extensively studied by TEM techniques, and form when the number of repeat periods exceeds a critical number.
