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The optical properties of GaAsN/GaAs heterostructures grown by molecular-beam epitaxy with different nitrogen content in the layers have been studied. The optical properties of GaAsN layers in the growth conditions under study are defined by the carrier recombination via localized states related to a strong composition inhomogeneity in the solid solution. The increasing of the nitrogen content raises the composition inhomogeneity and the carrier localization energy. [ABSTRACT FROM AUTHOR]

Structures with In(Ga)As quantum dots in the GaAs matrix obtained using molecular-beam epitaxy are investigated using photoluminescence (PL) measurements and transmission electron microscopy. The structures were subjected in situ to the procedure of the selective thermal elimination of defect regions. Based on the results of the analysis of luminescence properties, a method for evaluating the crystalline quality of structures using the measurements of PL intensity for the GaAs matrix at high temperatures (as high as 400 K) is suggested. Procedures for the elimination of defects are investigated, namely, the single-stage selective elimination of InAs defect islands at 600°C and a two-stage procedure. The latter procedure additionally includes selective overgrowth with a thin AlAs layer and high-temperature (650-700°C) heat treatment. The optimal conditions of the process, which permit the obtaining of structures with a relatively low defect density without a considerable decrease in the density of coherent quantum dots, are found. [ABSTRACT FROM AUTHOR]

Optical properties of structures with vertically coupled quantum dots grown by the combined submonolayer molecular-beam epitaxy were investigated. It is shown that the formation of the laterally coupled conglomerates of quantum dots are possible in upper rows for certain parameters of growth, with the corresponding photoluminescence emission being in the wavelength range of 1.3-1.4 µm at room temperature. [ABSTRACT FROM AUTHOR]

The influence of the growth conditions during molecular-beam epitaxy and of the degree of lattice mismatch between the epilayer and the substrate on the formation of InGaAs islands on a Si(100) surface is studied. An increase in lattice mismatch (the InAs mole fraction) leads to an increase in the critical thickness corresponding to the onset of island growth, in contrast to the formation of InGaAs islands on GaAs(100). An increase in the deposition temperature also increases the critical thickness, whereas an increase in the arsenic pressure has the opposite effect. Structures containing an array of InGaAs islands in a Si matrix display a luminescence line in the range 1.2-1.3 µm, depending on the mole fraction of InAs. [ABSTRACT FROM AUTHOR]

The optical properties of structures containing InGaAs quantum dots in GaAs and AlGaAs matrices grown by molecular-beam epitaxy are investigated. It is shown that increasing the In content in the quantum dots has the effect of raising the energy of carrier localization and increasing the energy distance between the ground state and the excited states of carriers in the quantum dots. An investigation of the influence of postgrowth annealing on the optical properties of the structures shows that the formation of vertically coupled quantum dots and the use of a wide-gap AlGaAs matrix enhances the thermal stability of the structures. Moreover, high-temperature (830°C) thermal annealing can improve the quality of the AlGaAs layers in structures with vertically coupled InGaAs quantum dots in an AlGaAs matrix. The results demonstrate the feasibility of using postgrowth annealing to improve the characteristics of quantum dot lasers. [ABSTRACT FROM AUTHOR]

Arrays of strained InAs islands in an (In, Ga)As matrix on an InP(100) substrate are synthesized by molecular-beam epitaxy, and their structural and optical properties are investigated. According to transmission electron microscope and high-energy electron diffraction data, the critical thickness corresponding to the onset of island growth is 3 monolayers. The resulting InAs islands are coherently strained, and their base diameter varies from 20 nm to 90 nm. The formation of islands produces in the photoluminescence spectra a dominant long-wavelength line, which shifts toward lower energies as the effective thickness of the InAs increases. The radiation emitted by the InAs islands spans a wavelength range of 1.65-2 µm. [ABSTRACT FROM AUTHOR]

The influence of mismatch stress on the structural, optical, and transport properties of thick InGaAs layers grown on InP(100) substrates by molecular-beam epitaxy is investigated. It is found that layers having tensile stress can be grown with a greater mismatch than compressively stressed layers before plastic relaxation sets in. The critical mismatch for thick InGaAs layers is not described with sufficient accuracy by either the mechanical equilibrium model or the energy balance model. The range of mismatches required to obtain high carrier mobilities and high radiative recombination efficiencies in InGaAs layers grown on InP substrates is much narrower than the pseudomorphic growth range. The maximum mobilities and minimum widths of the photoluminescence peak are attained in layers matched with the substrate in terms of the lattice parameter and also in slightly gallium-enriched layers. The compositional dependence of the width of the band gap is investigated with allowance for the influence of stress. © 1997 American Institute of Physics. [ABSTRACT FROM AUTHOR]

It is shown that an array of two-dimensional islands is formed during the growth of ultrathin (∼1.5 monolayers) InSb layers on a GaSb (100) surface by molecular beam epitaxy. After the deposition of several InSb layers separated by narrow barriers, islands of subsequent rows are formed on top of islands of the first row (vertical correlation effect). The formation of islands is confirmed by analysis of the photoluminescence spectra. [ABSTRACT FROM AUTHOR]

Molecular beam epitaxy was used to fabricate GaAsN/GaAs and InGaAsN/GaAs heterostructures, and the influence of the growth regimes on their characteristics was studied. It is shown that implantation of nitrogen causes a substantial long-wavelength shift of the radiation. The possibility of obtaining 1.4 µm radiation at room temperature was demonstrated using In[sub 0.28]Ga[sub 0.72]As[sub 0.97]N[sub 0.03]/GaAs quantum wells. [ABSTRACT FROM AUTHOR]

InAs/InGaAsN quantum dots have been grown by molecular beam epitaxy on GaAs substrates. Transmission electron microscopy shows the increase in the island size as compared to the InAs/InGaAs quantum dots. Room temperature photoluminescence at 1.55 μm has been demonstrated whose intensity was comparable to that of the InGaAsN/GaAs quantum wells emitting at 1.3 μm. The effect of nitrogen concentration on the PL peak position and intensity has been studied. [Copyright &y& Elsevier]