Influence of a thin GaAs cap layer on structural and optical properties of InAs quantum dots

In this letter we investigate the changes in the surface morphology and emission wavelength of InAs quantum dots (QDs) during initial GaAs encapsulation by atomic force microscopy and photoluminescence. The density (2.9x10(10) cm(-2)) and height (7.9+/-0.4 nm) of the uncapped QDs decrease and saturate at 0.6x10(10) cm(-2) and 4 nm, respectively, after the deposition of 4 monolayers (MLs) of GaAs. A model for the evolution of surface morphology is proposed. Photoluminescence spectra of the surface dots show a wavelength shift from 1.58 to 1.22 mum when the GaAs capping layer thickness increases from 0 to 8 MLs. (C) 2002 American Institute of Physics.