Atomic Force Microscopy of Ingan-Based Structures Grown by Metal-Organic Vapour Phase Epitaxy

Atomic force microscopy was used to characterise InGaN-based structures grown by metal-organic vapour phase epitaxy at temperatures between 760 and 860 degreesC. The samples studied included thick InGaN layers, and InGaN/GaN multiple quantum wells (MQWs) on both conventional GaN buffer layers and a GaN template layer produced by epitaxial lateral overgrowth (ELOG). Pits, of inverted hexagonal pyramidal form, were observed on surfaces of these MQW samples, which contain 5-18 wells. The majority types of threading dislocations (TDs), with pure edge or mixed character, appear to nucleate these V- pits. A laterally varying V-pit density was observed on the MQW grown on the ELOG template, correlating with the TD distribution in the GaN below the MQW. InGaN epilayers show microscopically rough surfaces dissimilar to either MQWs or GaN buffer layers.