Photoluminescence (PL) spectra of interband transitions in GaInNAs/GaAs single quantum wells grown by, metalorganic chemical vapor deposition technique on semi-insulating GaAs substrates were measured at 77 K for several samples grown with different In composition and dimethylhydrazine.(DMH)/III ratios. The results show that the PL intensity increases as the In mole fraction is increased from 0 to 25%, but the PL intensity is degraded for samples with an In mole fraction of 30% or higher. The peak position energies of the PL spectra were investigated as a function of the DMH/III ratio. Thermal annealing effect induced a blue-shift in the PL spectra peak position energy in samples grown with high DMH/III ratio.

Photoluminescence (PL) spectra of interband transitions in GaInNAs/GaAs single quantum wells grown by metalorganic chemical vapor deposition on semi-insulating GaAs substrates were measured at 77 K for several samples grown with different In compositions and dimethylhydrazine (DMH)/III ratios. The results show that the PL intensity increases as the In mole fraction is increased from 0% to 25%, but the PL intensity is degraded for samples with an In mole fraction of 30% or higher. The peak position energies of the PL spectra were investigated as a function of the DMH/III ratio. Thermal annealing effect induced a blueshift in the PL spectra peak position energy in samples grown with high DMH/III ratios.

GaAs(311) surfaces grown by molecular beam epitaxy are investigated by in situ ultrahigh-vacuum scanning tunnelling microscopy. The observation of an atomically flat Ga(2x1)-reconstructed GaAs(311) surface and its transformation to a 8x1-reconstructed GaAs(311) surface leads to an improved understanding of the processes involved in the step formation. The high density of steps observed on the 8x1-reconstructed GaAs(311) surface along the [(2) over bar 33] direction originates from the change of surface atomic density required to accommodate the surface transition from the Ga(2x1) surface to the 8x1 surface. This understanding is further supported by the observation of independent step formation.

We report on the influence of the chemical composition of the (Al, Ga)As surface on the formation of strain induced three-dimensional (3D) InAs islands. The experiments have been carried out using a molecular beam epitaxy facility combined with a scanning tunneling microscope enabling in situ surface characterization. The evolution of the density and morphology of these islands is investigated as a function of the Al composition. The InAs deposition, substrate temperature, and annealing time effects on the island formation and morphology are studied. The morphologies of the (Al, Ga)As surface as well as that of the reconstructed InAs “wetting layer” are also described. Results indicate that there are major differences between the InAs/GaAs and the InAs/AlAs systems despite the same lattice mismatch. We observe these differences varying the aluminum content in the starting (Al, Ga)As surface. We show that control of the Al fraction leads to control of the size and density of the 3D islands. The control of island density and size as well as the growth mode of these islands is explained by considering the difference in surface mobility and cation intermixing between these two systems. Our observation is that strain energy is not the only parameter governing the formation of 3D islands but the chemical nature of the different layers involved is proved to significantly affect island properties.

We present an investigation of the morphology of InP/GaInP three-dimensional (3D) islands obtained by molecular beam epitaxy. This material system should represent the counterpart of the InGaAs/GaAs system for the visible range. The islands are found to be truncated pyramids with observable phosphorous-rich surface reconstruction on top. The investigation of the effect of P overpressure reveals a path to achieve extremely homogeneous 3D islands through an island shape transition. These results help us understand the emerging issue of 3D island shape transition.

We have used in-situ scanning tunneling microscopy (STM) to study the formation and evolution of InAs islands on an InP (001) surface. The InAs islands are produced by (i) exchange of P-atoms with As-atoms or by (ii) direct deposition of In and As. In both cases InAs nanowires arem elongated along the [ī 10] direction with a length over 1 µm. We observe these nanowires to be stable under an arsenic environment while unstable with no arsenic flux, and eventually transform into a rectangular-based pyramid with a truncated top. These observations indicate that surface reconstruction can play a role in the selection of quantum wire or dot growth.