Influence of the cap layer on the Gibbs free energy above a layer of buried InGaAs islands

The Gibbs free energy above a layer of buried In x Ga 1−x As islands embedded in a GaAs cap layer is calculated as a function of the cap thickness and mole fraction of the dots. The model is based on a three-dimensional calculation of the elastic strain within the continuum elastic theory. A surface map of the Gibbs free energy due to strain variations is a useful guide in understanding the vertical ordering of dots as well as cooperative nucleation in the lateral direction. The calculated results have implications for determining how thick a cap layer can be before preferential nucleation above a layer of buried stressors ceases. Additionally, the Gibbs potential depth is estimated for varying In composition of the buried pyramidal stressors. It is found that even a slight change in the shape of the island can influence the degree of screening that the GaAs cap exerts on the Gibbs potential.