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  • 1
    Electronic Resource
    Electronic Resource
    Simultaneous experimental evaluation of In and N concentrations in InGaAsN quantum wells (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 3792-3798 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We propose a method that solves the problem of the independent determination of the indium and nitrogen concentrations in a strained quaternary InGaAsN superlattice. The method is experimentally based on the simultaneous measurement: (i) of the tetragonal lattice distortion of the unit cell from high resolution micrographs and (ii) of the intensity of the chemically sensitive (002) reflection from dark field images. As an example, we evaluate InGaAsN quantum wells with a nominal N concentration of 1.7% and with In concentrations of 10%, 20%, or 35%. We reveal local fluctuations of the In and N concentrations over distances down to 4 nm with a sensitivity of 0.1% for N and 1% for In fluctuations in this distance range. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1402139
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  • 2
    Electronic Resource
    Electronic Resource
    Strained state of Ge(Si) islands on Si: Finite element calculations and comparison to convergent beam electron-diffraction measurements (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 3617-3619 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this letter we present calculations by three-dimensional finite element method and measurements by convergent beam electron diffraction of the displacement field resulting from misfitting Ge0.85Si0.25 islands on Si(001). A good agreement between the results of both methods indicates that the three-dimensional finite element method is a reliable tool to calculate the strain, and thus the stress field, in such nanostructures. As a result both methods show that the substrate substantially takes part in the elastic relaxation process in such heteroepitaxial systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111217
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of growth conditions on the structural properties of ion beam sputter deposited SiGe epilayers (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 4975-4981 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Structural properties of Si1−xGex layers epitaxially grown on Si(100) by Ion Beam Sputter Deposition were studied as a function of growth temperature and film thickness. It was shown that the structure of defects strongly depends on the growth temperature, Tg. The dislocations cross grid which is observed at the SiGe/Si interface for layers grown at high (700 °C) Tg is missing in layers grown at low ((approximately-less-than)550 °C) Tg, while a new type of defects parallel to {001} and {113} lattice planes appear at these temperatures. The optimal Tg for a Ge content of 20-25 at. % was found to be close to 550-625 °C. Surface roughness for all the growth temperatures was found to be less than that for such a "smooth'' technique as MBE. Photoluminescence studies revealed, to the best of our knowledge for the first time, two peaks on the low energy side in the neighborhood of the Si(TO) peak of the epilayers. The evolution of the intensity of these peaks is strongly correlated with the dynamics of strain relaxation and can be attributed to a set of dislocations at the SiGe/Si interface extending both to the epilayer and to the bulk Si. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359788
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  • 4
    Electronic Resource
    Electronic Resource
    Carrier recombination at single dislocations in GaN measured by cathodoluminescence in a transmission electron microscope (2002)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 92 (2002), S. 2000-2005 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We study radiative and nonradiative recombination at individual dislocations in GaN by cathodoluminescence performed in a transmission electron microscope. The dislocations are produced by indentation of dislocation free single crystals and have a-type Burgers vectors (b=1/3〈112¯0〉). They are aligned along 〈112¯0〉 directions in the basal plane. Our direct correlation between structural and optical properties on a microscopic scale yields two main results: (i) 60°-basal plane dislocations show radiative recombination at 2.9 eV; (ii) screw-type basal plane dislocations act as nonradiative recombination centers. We explain the nonradiative recombination by splitting this dislocation into 30° partials that have dangling bonds in the core. The dissociation width of these dislocations is 〈2 nm. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1490618
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  • 5
    Electronic Resource
    Electronic Resource
    Microscopic nature of the Er3+ emission in mixed amorphous-nanocrystalline Si:H films (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 2773-2780 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: ErO6 complexes, where every Er3+ ion is surrounded by six oxygen atoms forming an octahedron with C3v point symmetry, are found to best describe the strong Stark splitting of the characteristic Er3+ emission in the 1460–1610 nm range. An a-Si:H matrix serves as an ideal semiconductor host to permit codoped O atoms to form an optimal octahedral ligand field around the Er3+ ions. The observation of sharp intense Stark peaks for temperatures between 153 and 300 °C and of strong enhancement of the Er3+ emission after 350 °C annealing can be understood first by diffusion and then outdiffusion of weakly bound hydrogen atoms in the a-Si matrix. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1388564
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  • 6
    Electronic Resource
    Electronic Resource
    Strain-induced island scaling during Si1−xGex heteroepitaxy (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 179-181 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigated the composition-dependent size of pseudomorphic Si1−xGex islands on Si(001). Si1−xGex layers with 0.05≤x≤0.54 were deposited from metallic solution. The island growth occurs near thermodynamic equilibrium and facilitates a comparison of the results with predictions based on energetics. We find pseudomorphic islands with base widths ranging from several μm to a few nm. We show that it is possible to adjust the island size by simply choosing the appropriate layer composition. Varying deposition temperatures and growth velocities do not affect the scaling behavior. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120622
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  • 7
    Electronic Resource
    Electronic Resource
    Misfit grainlets: Point strain sources compensating misfit during epitaxial growth (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 952-954 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We propose a misfit relaxation mechanism that may occur during growth in highly misfitting layers. It is based on a misfit compensating distribution of physical point strain sources at the interface between layer and substrate instead of misfit dislocations. These point strain sources are realized by interfacial islands (misfit grainlets) that have a lattice misfit opposite in sign to that of the surrounding epitaxial layer, in most cases brought about by an orientation relationship different from that of the surrounding layer to the substrate. We demonstrate the effectiveness in strain relaxation of misfit grainlets with an analysis of the interface structure of GaN on sapphire and discuss the formation of misfit grainlets in terms of a self-organized island growth process. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118451
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  • 8
    Electronic Resource
    Electronic Resource
    Surface ripples, crosshatch pattern, and dislocation formation: Cooperating mechanisms in lattice mismatch relaxation (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 1232-1234 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We study the interplay of elastic and plastic strain relaxation of SiGe/Si(001). We show that the formation of crosshatch patterns is the result of a strain relaxation process that essentially consists of four subsequent stages: (i) elastic strain relaxation by surface ripple formation; (ii) nucleation of dislocations at the rim of the substrate followed by dislocation glide and deposition of a misfit dislocation at the interface; (iii) a locally enhanced growth rate at the strain relaxed surface above the misfit dislocations that results in ridge formation. These ridges then form a crosshatch pattern that relax strain elastically. (iv) Preferred nucleation and multiplication of dislocations in the troughs of the crosshatch pattern due to strain concentration. The preferred formation of dislocations again results in locally enhanced growth rates in the trough and thus leads to smoothing of the growth surface. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115017
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  • 9
    Electronic Resource
    Electronic Resource
    Dislocation glide in {110} planes in semiconductors with diamond or zinc-blende structure (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 2206-2208 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The activation of the secondary a/2〈110〉{110} glide systems as observed by transmission electron microscopy in epitaxial Ge(Si) and InGaAs layers grown on comparatively highly misfitting substrates, is rationalized in terms of a mechanical equilibrium analysis that includes a frictional force on the gliding dislocations. The conditions for occurrence of further secondary glide planes, such as {113} and {100}, are outlined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109443
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  • 10
    Electronic Resource
    Electronic Resource
    Reduced effective misfit in laterally limited structures such as epitaxial islands (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 574-576 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Numerical finite element calculations have been reported to determine a correction function Φ that describes the reduction of the misfit that occurs when laterally limited structures such as faceted islands or mesa structures are grown on a substrate. The reduction of the average strain energy density is calculated in these three-dimensional islands and compared to the constant strain energy density in a continuous layer. Ratios Φ are obtained from the calculation of different island geometries, i.e., different facet angles γ and different aspect ratios island width l to island height h. These discrete values are fitted by a function which can easily be applied to the full range of aspect ratios (l/h(approximately-greater-than)0) and facet angles (0°〈γ〈90°). Faceted Ge(Si) islands on Si(001) substrate, grown from the solution in the Stranski–Krastanov growth mode, serve as an example for the calculation. Experimental and theoretical values for the critical thickness of these islands agree well. This result demonstrates the drastic influence of islanding on misfit strain distribution in island and substrate as well and, consequently, on the strong increase of the critical thickness as determined by the mechanical equilibrium theory of Matthews and Blakeslee. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114017
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