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

Abstract
In this letter we investigate the changes in the surface morphology and emission wavelength of InAsquantum dots(QDs) during initial GaAs encapsulation by atomic force microscopy and photoluminescence. The density (2.9×10 10 cm −2 ) and height (7.9±0.4 nm ) of the uncapped QDs decrease and saturate at 0.6×10 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 μm when the GaAs capping layer thickness increases from 0 to 8 MLs.