Optical investigation of the self-organized growth of InAs/GaAs quantum boxes

By studying the optical properties of highly strained InAs/GaAs multilayers as a function of the deposited quantity of InAs, a high resolution probing of the change from two-dimensional to three-dimensional morphology of the InAs layers has been performed. We show that the critical thickness for the onset of three-dimensional growth is very well defined for given growth conditions. The nucleation of the islands is, however, asynchronous, due to the spatial fluctuations of the deposited quantity of InAs. A fast initial growth of the InAs islands leads within a few seconds to a quasi-equilibrium morphology for InAs. Asynchronous nucleation and fast initial growth combined are shown to be the major origin of the size fluctuations of InAs quantum boxes in GaAs obtained by self-organized growth under standard molecular beam epitaxy (MBE) growth conditions.