Strain Relaxation of Self-Assembled InAs/GaAs(001) Quantum Dots Observed by Reflection High-Energy Electron Diffraction

Strain relaxation of self-assembled InAs quantum dots on GaAs (001) surface was investigated by in situ reflection high-energy electron diffraction (RHEED) during molecular-beam epitaxy (MBE). Relaxed atomic structures of a dot, wetting layer and substrate system were calculated for several shapes and sizes of dots using the Stillinger-Weber strain potential. The surface-parallel lattice parameter averaged in each atomic layer of the dot increases from the bottom layer to the top layer. A scale invariance of the strain distribution was found for the typical InAs-dot sizes when the shape of the dot is fixed. By taking into account the attenuation of an electron beam it was shown that the variation of the mean lattice parameter of the dots measured by RHEED depends mainly on the dot coverage (area density of atoms in all dots) and the height/diameter ratio of the dots.