Study of the molecular beam epitaxial growth of InAs on Si-covered GaAs(1Â 0Â 0) substrates

The molecular beam epitaxial growth of InAs on GaAs (1 0 0) surfaces exposed to a Si-flux has been investigated. We varied the Si-coverage (ΘSi) of the GaAs surface from 0 to 1.0 monolayers (ML), and studied the effects on the self-assembling of InAs nanoislands. It was found that for ΘSi equal to 0.3 and 0.6 ML, Si induces a bimodal size distribution that is associated to the creation of nucleation centers. We observed, that the inclusion of such nucleation centers changes the strain relaxation of the deposited InAs as compared with the sample grown with ΘSi=0. For ΘSi=1, we found that the three-dimensional (3D) islands start to nucleate from the very early stages of InAs deposition resembling the Volmer-Weber growth, contrasting with the usual Stranski-Krastanov growth mode of InAs on uncovered GaAs (1 0 0) substrates. For this sample the 3D growth mode is prompted by strain fields originated when Si is incorporated at the InAs-GaAs interface as an interlayer, as well as by the passivation of the GaAs surface by As-Si bonds. Atomic force microscopy images of the samples as well as reflectance difference spectroscopy also showed evidences of the InAs modified growth behavior. The GaAs interband transitions observed in the reflectance difference spectroscopy (RDS) spectra shifts in energy presumable due to changes in the strain status of the GaAs surface.