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  • Articles  (106)
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  • Articles  (106)
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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 7427-7430 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Deep level transient spectroscopy (DLTS) was performed on p-isotype Si/SiGe/Si Schottky barrier diodes in order to obtain the valence band offset between Si and SiGe. A single strained Si0.7Ge0.3 layer was placed in such a depth in Si so as to be able to fill and empty the quantized SiGe well during the transient capacitance procedure. Broad capacitance transient peaks were obtained and interpreted as being due to the capture of holes by the quantum well. The broadness of the peaks was explained by thickness variations of the SiGe layer. From the dependence of the high temperature side of the DLTS peak on the rate window a valence band offset of 220±20 meV was evaluated.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 5113-5118 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The influence of molecular hydrogen (H2) on the structural and optical properties of self-assembled Ge dots grown on Si(001) has been studied using atomic force microscopy and photoluminescence spectroscopy (PL). Without hydrogen, a well known bimodal island size distribution occurs with small {105} faceted pyramids, and larger multifaceted domes. In the presence of an additional H2 flow, we observe that a higher density of smaller pyramids and a lower density of domes occurs. Moreover, in the presence of hydrogen, PL investigations have revealed a thicker wetting layer thickness, probably due to a reduction of the surface diffusion length. © 2000 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 7275-7282 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article we study the electroluminescence of p-i-n diode structures with Ge dots consisting of coherent three-dimensional small (pyramids) and larger (dome) islands. The Ge dots are formed through strain-induced islanding. The diode structures, including one layer with Ge dots, were deposited on Si mesas with variable areas in order to study the influence of limited area deposition on self-assembling. It was observed that the reduction of deposited area improves island uniformity. The combined analysis of island distribution and electroluminescence spectra has lead to the conclusion that domes in small diodes have a smaller Si content or are less relaxed than domes in larger diodes. The diodes are found to emit up to room temperature near the optical communication wavelength of 1.3 microns. © 2000 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 6709-6715 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Among the growth approaches being considered currently to realize quantum dots and quantum wires is the selective epitaxial growth on patterned substrates. With this technique the feature size and geometry are mainly limited by the lithographic process. With optical lithography we achieved a lateral dimension of ≥0.4 μm. Therefore, to further reduce the lateral dimension, but still using optical lithography, the tendency toward facet formation during selective epitaxial growth was investigated. Si0.70Ge0.30 multiple quantum well structures with Si0.935Ge0.065 spacers and buffers were deposited on (001) Si. The buffer thickness was varied so as to achieve facet junction. While on large areas the Si0.935Ge0.065 buffer was relaxed, for dots ≤300 μm or narrower the structures remained strained even for buffer thicknesses exceeding by a factor of two–three the critical thickness of large area. In dots and wires where facet junctioning has taken place a rounded region between facets (approximately 50 nm broad) in the quantum well layers was observed. In wires oriented parallel to 〈100〉 sidewalls self-organized wire formation and vertical correlation of these growth induced wires was observed. The photoluminescence of all dots and wires down to the lowest achieved dimension and including the self-organized wires is strong, with the integral intensity normalized to the surface coverage for 100 nm dots exceeding by a factor of 50 the emission from unpatterned areas. © 1997 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 5439-5447 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the determination of the valence band offset between strained Si1−xGex and unstrained Si layers by deep level transient spectroscopy (DLTS) on Si/Si1−xGex/Si quantum well (QW) structures. A problem of this technique is to store the holes long enough (≥1 ms) in the QW so that the thermal emission of holes is the dominating process. We achieved sufficiently long hole storage times by using two different structures. In the first ones, this is obtained by selective growth which leads to a lateral limitation of the smooth QW layer, and with good Schottky contacts. For the second ones, the localization of holes is due to the presence of Si1−xGex islands. For a sample containing a smooth QW with XGe=0.17 a valence band offset of 140±20 meV was obtained and for the island layer with XGe=0.3 a value of 258±20 meV was found. These results are in good agreement with theory. The DLTS measurements are compared to admittance spectroscopy results and photoluminescence measurements. © 1995 American Institute of Physics.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 811-816 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experimental and theoretical evidence is given for the occurrence of a temperature and strain dependent roughening transition from two dimensional (2-D) monolayer to 3-D island growth in strained III-V compound ternary alloys and GeSi. For sufficiently large strain energy values the shape of the transition curve was found to follow a T∼ε−2f relationship, as predicted from classical nucleation theory arguments, where T is the growth temperature and εf the areal misfit strain energy. The asymptotic behavior in the zero strain energy regime could be reproduced by an empirical curve of a more complex expression. The transition curve appears to separate routes of strain relief in the above systems, which were found to predominantly follow 3-D island formation in the higher, and misfit dislocation formation in the lower growth temperature/strain regime. © 1995 American Institute of Physics.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 1959-1963 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: SiGe/Si quantum well layers are selectively grown by low pressure chemical vapor deposition on patterned Si substrates. Transmission electron microscopy (TEM) shows that the growth rate of SiGe in convex corners between different surface planes is at least ten times higher than the growth rate observed on (001) planes. This high growth rate leads to the formation of quantum wires and dots between such facets. Photoluminescence (PL) spectra of square and rectangular patterns, bounded by quantum wires, ranging in size from 300μm down to 500nm are taken. The observed energy shifts of the (001) quantum well PL–peaks are explained by surface diffusion of Ge adatoms into the quantum wires. A surface diffusion model is used to obtain a Ge diffusion length of λ=2.5±0.6 μm at 700°C. Thus, a method for the determination of surface diffusion lengths in strained layer epitaxy is introduced. For SiGe layers grown above the Stranski–Krastanow critical thickness for three dimensional (3D) growth, a competition between the SiGe wires in the interfacet corners and the SK islands on the (001) planes is observed. In squares as large as 2×2 μm2 the SiGe wires lead to a suppression of 3D growth on the (001) plane altogether, as observed by TEM and PL. © 1995 American Institute of Physics.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2463-2466 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have determined the valence band discontinuity ΔEv of strained Si1−xGex on unstrained (100) Si using temperature-dependent current–voltage characteristics (I–V-T) of Si/Si0.83Ge0.17/Si heterostructures. In a first step, the measurements were performed on a Schottky diode, and in a second step, on a sample with ohmic contacts. The values of ΔEv obtained by these two different procedures are comparable. Moreover, they are in good agreement with the theoretical value of ΔEv=0.84x=143 meV predicted by Van de Walle measurements. © 1996 American Institute of Physics.
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 2183-2185 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this letter we report photoluminescence and structural results obtained on asymmetrically strained Si0.7Ge0.3/Si single and multiple quantum wells epitaxially grown by low pressure chemical vapor deposition. Well-resolved peaks were obtained which can be attributed to quantum well excitons and their transversal optical phonon replica. A good correlation between peak properties and structure results was found. From the photoluminescence peak energies a valence band offset of 0.27 eV and an effective hole mass of 0.25 were estimated.
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 2409-2411 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The synthesis of buried CoSi2 layers in Si0.91Ge0.09 alloys by the implantation of high doses of 100 and 150 keV Co+ ions and subsequent rapid thermal annealing at T≥1000 °C is studied by x-ray diffraction, Rutherford backscattering spectroscopy, He ion channeling, Auger electron spectroscopy, and transmission electron microscopy. After annealing, a buried single-crystal CoSi2 layer containing ≈1 at. % Ge is formed in the SiGe alloy. Silicide formation causes an outdiffusion of Ge leading to an increase in the Ge concentration of the adjacent SiGe layers. The remaining Ge within the silicide layer is found to be present as Si-Ge islands with the composition of the virgin Si0.91Ge0.09 alloy.
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