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The shape of InAs nanostructures formed by molecular beam epitaxy on a (001) InP substrate in the Stranski-Krastanow growth mode is studied. A transition from wires to round-shaped islands is observed as a function of the amount of InAs deposited. It is attributed to the non-equivalent energies of the A and B facets existing in zinc blende materials (facets along [1 1 ¯ 0] and [110], respectively). This surface energy anisotropy is considered to determine the nanostructure equilibrium shape from the balance between the elastic energy and the surface energy. At low volumes, the most energetically favorable shape is the wire-like shape, while at high volumes, the equilibrium shape is the island-like shape. The calculated sizes for which the shape changes are in good agreement with experimental sizes. The low lattice mismatch and the low surface energy of (114)A InAs facets around 41 meV/A2, as obtained from density functional theory calculations, enhance this effect in the InAs/InP system. [ABSTRACT FROM AUTHOR]

Surfactant mediated growth of strained InAs/AlAs0.56Sb0.44 quantum wells on InP (001) substrate is investigated. X ray diffraction and transmission electron microscopy analysis reveal that the supply of antimony on InAs surface delays the 2D to 3D growth transition and allows the growth of thick InAs/AlAsSb quantum wells. Quantum well as thick as 7 ML, without defect was achieved by Sb surfactant mediated growth. Further high resolution transmission electron microscopy measurement and geometric phase analysis show that InAs/AlAsSb interfaces are not abrupt. At InAs on AlAsSb interface, the formation of a layer presenting lattice parameter lower than InP leads to a tensile stress. From energetic consideration, the formation of As rich AlAsSb layer at interface is deduced. At AlAsSb on InAs interface, a compressive layer is formed. The impact on optical properties and the chemical composition of this layer are discussed from microscopic analysis and photoluminescence experiments. [ABSTRACT FROM AUTHOR]

We report on Sb surfactant growth of InAs nanostructures on GaAs0.51Sb0.49 layers deposited on InP (001) and on (113)B oriented substrates. On the (001) orientation, the presence of Sb significantly favors the two-dimensional growth regime. Even after the deposition of 5 mono-layers of InAs, the epitaxial film remains flat and InAs/GaAs0.51Sb0.49 type-II quantum wells are achieved. On (113)B substrates, same growth runs resulted in formation of high density InAs islands. Microscopic studies show that wetting layer is missing on (113)B substrates, and thus, a Volmer- Weber growth mode is concluded. These different behaviors are attributed to the surface energy changes induced by Sb atoms on surface. [ABSTRACT FROM AUTHOR]