Spiral growth of InGaN nanoscale islands on GaN

Spiral growth was found to be the dominant growth mechanism for InGaN single quantum wells grown under low trimethylgallium flow rates by metal-organic chemical vapor deposition on GaN-on-sapphire films. This spiral growth around threading dislocations with a screw component led to the formation of flat, 1-2 nm high, InGaN islands of diameters in the range of 100-400 nm. The diameter of the InGaN islands increased with decreasing trimethylgallium flow, i.e., decreasing InGaN growth rate. The formation of spatially separated islands could be enhanced by disilane pre-treatment of the GaN surface prior to InGaN deposition. The InGaN island formation is discussed as a possible contribution to the development of spatial inhomogeneities in InGaN layers.