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  • 2010-2014  (19)
  • 2000-2004  (64)
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  • 1
    Digitale Medien
    Digitale Medien
    Phonon-Plasmon Interaction in Tunnelling GaAs/AlAs Superlattices Grown on (311) and (100) Substrates (2001)
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 82-84 (Nov. 2001), p. 581-586 
    Details
    ISSN: 1662-9779
    Quelle: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Thema: Physik
    Materialart: Digitale Medien
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/26/transtech_doi~10.4028%252Fwww.scientific.net%252FSSP.82-84.581.pdf
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  • 2
    Digitale Medien
    Digitale Medien
    Specifics of MOCVD formation of InxGa1−x N inclusions in a GaN matrix (2000)
    Springer
    Semiconductors 34 (2000), S. 621-625 
    Details
    ISSN: 1063-7826
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract MOCVD-grown heterostructures with one or several InxGa1−x N layers in a GaN matrix have been studied by transmission electron microscopy. In heterostructures with thick InGaN layers, a noncoherent system of domains with lateral dimensions (∼50 nm) on the order of the layer thickness (∼40 nm) is formed. In the case of ultrathin InGaN inclusions, nanodomains coherent with the GaN matrix are formed. The content of indium in nanodomains, determined by the DALI method, is as high as x≈0.6 or more, substantially exceeding the average In concentration. The density of the nanodomains formed in the structures studied is n≈(2–5)×1011 cm−2. In the structures with ultrathin InGaN inclusions, two characteristic nanodomain sizes are observed (3–6 and 8–15 nm).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1134/1.1188041
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  • 3
    Digitale Medien
    Digitale Medien
    Lasing in the vertical direction in InGaN/GaN/AlGaN structures with InGaN quantum dots (2000)
    Springer
    Semiconductors 34 (2000), S. 481-487 
    Details
    ISSN: 1063-7826
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik , Physik
    Notizen: Abstract InGaN/GaN structures with dense arrays of InGaN nanodomains were grown by metallorganic chemical vapor deposition. Lasing in vertical direction occurs at low temperatures, indicating ultrahigh gains (∼ 105 cm−1) in the active region. Fabrication of an effective AlGaN/GaN distributed Bragg reflector with reflectivity exceeding 90% enables vertical lasing at room temperature in structures with a bottom distributed Bragg reflector, despite the absence of a well-reflecting upper mirror. The lasing wavelength is 401 nm, and the threshold excitation density is 400 kW/cm2.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1134/1.1188011
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  • 4
    Digitale Medien
    Digitale Medien
    On the origin of the "coffee-bean" contrast in transmission electron microscopy images of CdSe/ZnSe quantum dot structures (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 4150-4155 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The origin of the "coffee-bean" strain contrast is studied, that is observed in the plan-view transmission electron microscopy (TEM) images of CdSe/ZnSe quantum dot structures. The samples were grown by two different methods: standard molecular-beam epitaxy at 350 °C and atomic layer epitaxy at 230 °C with annealing at 340 °C after the CdSe deposition. The nominal CdSe thickness was above 3 ML. In situ reflection high energy electron diffraction during the growth or during the annealing shows the transition from the two- (2D) into the three-dimensional (3D) surface morphology for both samples. The coffee-bean contrast is usually assigned to three-dimensional islands which are generated after the morphological 2D/3D transition. It is found that the coffee-bean contrast in plan-view TEM images is alternatively associated with pairs of stacking faults on {111} lattice planes which are inclined against each other. The stacking faults, which are bound by Shockley partial dislocations, are preferably generated in the vicinity of the Cd-rich regions (large islands) of the CdZnSe layer where Cd concentrations of more than 40% are found. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1352028
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  • 5
    Digitale Medien
    Digitale Medien
    Growth and vertical correlation of CdSe/ZnSe quantum dots (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 3695-3699 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The growth and vertical organization of CdSe quantum dots in three-layer stacks consisting of CdSe with a nominal thickness of 2.5 monolayers (ML) and ZnSe spacers with thicknesses between 10 and 20 ML was investigated by reflection high energy electron diffraction during the growth and different transmission electron microscopy techniques. The samples were grown by molecular beam epitaxy at 400 °C. It was found that up to 10 ML spacer thickness all three CdSe layers and ZnSe spacers form one broad (Cd, Zn)Se alloy layer with a small Cd concentration containing Cd-rich islands with a size of ∼15 nm. For spacers with a larger thickness (12–20 ML) three separated ternary (Cd, Zn)Se layers are observed which contain Cd-rich inclusions (small islands) with a size of less than 10 nm. A preferential vertical correlation of the small islands occurs for the 12 ML spacer thickness. With increasing spacer thickness, the number of the correlated small islands is reduced displaying a tendency to uncorrelated growth. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1352676
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  • 6
    Digitale Medien
    Digitale Medien
    Influence of the growth procedure on the Cd distribution in CdSe/ZnSe heterostructures: Stranski–Krastanov versus two-dimensional islands (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 81 (2002), S. 640-642 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Molecular beam epitaxy is used to grow different types of ZnSe/CdSe/ZnSe heterostructures. The topography of the bare CdSe surface studied with in situ atomic force microscopy is compared with high-resolution transmission electron microscopy data on overgrown structures. The growth procedure critically influences morphology and Cd distribution. Only use of thermal activation after low-temperature CdSe deposition enables the accomplishment of a distinct Stranski–Krastanov (SK) morphology with three-dimensional islands with a core of pure CdSe. Interdiffusion effects during activation of the SK transition as well as overgrowth are of minor importance. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1496133
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  • 7
    Digitale Medien
    Digitale Medien
    Influence of metalorganic chemical vapor deposition growth conditions on In-rich nanoislands formation in InGaN/GaN structures (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 2099-2101 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The influence of different growth conditions on the In distribution in ultrathin InGaN insertions in a GaN matrix is investigated by high-resolution transmission electron microscopy and an appropriate image evaluation technique. It is demonstrated that the indium distribution represents dense arrays of In-rich nanodomains inserted in a layer with a lower indium concentration. The sizes of the In-rich regions are about 4–5 nm at a growth temperature of 720 °C. Increasing the growth temperature leads to a strong decrease in the of nanoisland density and, also, a moderate decrease in their lateral size. Increasing the trimethylindium/trimethylgallium ratio strongly increases the density of the islands, but the lateral size remains weakly effected. The observations are in agreement with a thermodynamic model of island formation including entropy effects. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1462868
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  • 8
    Digitale Medien
    Digitale Medien
    Investigation of In segregation in InAs/AlAs quantum-well structures (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 4426-4428 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: In this letter, we report the investigation of In segregation in InAs/AlAs heterostructures. InAs layers with different thicknesses were grown by molecular beam epitaxy on GaAs (001) substrates. The layers were investigated by transmission electron microscopy. Profiles of the chemical composition of the InAs layers in the [001] direction were deduced from high-resolution lattice fringe images using the composition evaluation by lattice fringe analysis method. The segregation efficiency was derived by fitting the measured In concentration profiles with the segregation model of Muraki et al. [K. Muraki et al., Appl. Phys. Lett. 61, 557 (1992)]. We obtain efficiency of R=0.77±0.03 for the segregation of In in AlAs/InAs at a temperature of 530 °C. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1427148
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  • 9
    Digitale Medien
    Digitale Medien
    InGaN composition and growth rate during the early stages of metalorganic chemical vapor deposition (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 2552-2554 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy were applied to study the metalorganic chemical vapor deposition of InGaN and the correlation between the structural properties and luminescence of GaN/InxGa1−xN-quantum well structures. A series of samples was grown varying only the growth duration for the InGaN under otherwise unaltered growth conditions. Composition analyses were carried out by measuring local lattice parameters from TEM images, which are directly related to the local In concentration. A rising average In concentration from 6.5% to 15.4% and a decreasing growth rate are observed with increasing growth duration. All samples show an inhomogeneous In distribution containing In-rich agglomerates with a size of only a few nanometers and less pronounced composition fluctuations on a scale of some 10 nm. The redshift of the PL peak energy with increasing quantum well thickness indicates that the luminescence is predominantly determined by the piezoelectric field. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1409949
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  • 10
    Digitale Medien
    Digitale Medien
    Ordered arrays of vertically correlated GaAs and AlAs quantum wires grown on a GaAs(311)A surface (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 81 (2002), S. 1080-1082 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We study GaAs–AlAs short-period superlattices (SPSLs) grown on a GaAs(311)A surface using plan-view transmission electron microscopy (TEM). A strong in-plane compositional modulation with a period of 3.2 nm along the [01¯1] direction is revealed by TEM under chemically sensitive imaging conditions and in high-resolution TEM. Our results confirm the formation of highly ordered vertically aligned arrays of GaAs and AlAs quantum wires formed via self-organized growth. Bright photoluminescence (PL) at room temperature in the green and yellow spectral range is observed. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1497994
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