Surface transition induced island formation on thin strained InGaN layers on GaN (0001) in metal-organic vapour phase epitaxy

The surfaces of thin strained InGaN layers were investigated in metal-organic vapour phase epitaxy as a function of layer thickness and indium content. Even at layer thickness below 1 nm the surface exhibited 1−2 monolayer high irregular islands with diameters larger than twice the terrace spacing. Such islands are not observed on GaN grown at similar conditions. In-situ ellipsometry indicates a surface transition at the start and end of growth. During growth the surface contains about 1.5 monolayer of metal. We present two models that explain how a surface transition could form these islands.