Kinetic aspects of the morphology of self-assembled InAs quantum dots on GaAs(001)

We analyzed by atomic force microscopy self-assembled quantum dots of InAs on GaAs(001) in a series of samples prepared by molecular beam epitaxy (MBE). Two different growth procedures have been applied, namely, the usual continuous growth and the migration-enhanced growth. At equal depositions of InAs, larger than the critical thickness for the two- to three-dimensional transition, marked differences are found in the evolution of the nanoparticle density and volume, despite of the same set of growth parameters were used. Above 2 ML, a small fraction of ripened islands is also present, which is responsible for the nonlinear increase of the total volume of the dots with InAs coverage caused by an anomalous participation of the underlying layers. The different morphologies obtained substantiate the overwhelming role of kinetics on thermodynamics in the nonequilibrium MBE growth.