A finite-element study of strain fields in vertically aligned InAs islands in GaAs

Abstract

Finite-element calculations are used to study strain fields in vertically aligned InAs islands in GaAs. Such strain fields are found to be quite different from those of uncovered islands and nearly insensitive to the position of the island in the stacking. The driving force for vertically self-organized growth is known to be the interacting strain fields induced by the islands. The calculation of strain fields by the finite-element method makes it possible to model the correlations between adjacent InAs layers. A kinetic approach based on the effect of strain on surface diffusion is first proposed. A thermodynamic model is then analyzed to predict local island nucleation probabilities. Pairing probabilities of correlation between stacked islands, first calculated in the case of the InAs/GaAs system, are extended to the case of III-V semiconductors with a cubic crystalline structure. They are shown to be essentially dependent both on the ratio between the spacer layer thickness and the island height and on the lattice mismatch between islands and spacer layers.