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  • 1
    Electronic Resource
    Electronic Resource
    Temperature and strain dependence of the roughening transition in III-V semiconductor and SiGe epitaxial growth (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 811-816 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360270
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  • 2
    Electronic Resource
    Electronic Resource
    Growth of SiGe quantum wires and dots on patterned Si substrates (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 1959-1963 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358830
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  • 3
    Electronic Resource
    Electronic Resource
    Lateral confinement by low pressure chemical vapor deposition-based selective epitaxial growth of Si1−xGex/Si nanostructures (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 6709-6715 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365212
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  • 4
    Electronic Resource
    Electronic Resource
    Thermal hole emission from Si/Si1−xGex/Si quantum wells by deep level transient spectroscopy (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 5439-5447 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359658
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  • 5
    Electronic Resource
    Electronic Resource
    Determination of valence band offsets from Si/Si1−xGex/Si using temperature-dependent current–voltage characteristics (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 2463-2466 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361174
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  • 6
    Electronic Resource
    Electronic Resource
    Influence of molecular hydrogen on Ge island nucleation on Si(001) (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 5113-5118 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1317245
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  • 7
    Electronic Resource
    Electronic Resource
    Size distribution and electroluminescence of self-assembled Ge dots (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 7275-7282 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.372980
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  • 8
    Electronic Resource
    Electronic Resource
    Photoluminescence and microstructure of self-ordered grown SiGe/Si quantum wires (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 1888-1890 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Employing self-ordered growth in convex corners of nonplanar Si substrates, SiGe quantum wires of approximately 30 nm lateral dimension were fabricated. Photoluminescence spectra of these structures are dominated by transitions originating from the quantum wires at measurement temperatures above 20 K. The energetic positions of the quantum wire transitions are in good agreement with Ge concentrations measured by spatially resolved energy dispersive x-ray spectroscopy using a scanning transmission electron microscope. We find that the Ge concentration inside the wire is considerably lower than the nominal value for growth on planar parts of the substrate. In addition we find a pronounced gradient in the Ge concentration of the wire. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114366
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  • 9
    Electronic Resource
    Electronic Resource
    Determination of the valence band offset of Si/Si0.7Ge0.3/Si quantum wells using deep level transient spectroscopy (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 7427-7430 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353984
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  • 10
    Electronic Resource
    Electronic Resource
    Size distribution of Ge islands grown on Si(001) (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 410-412 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Atomic force microscopy analyses were performed on Ge islands on Si(001) grown by low pressure chemical vapor deposition in the temperature range from 525 to 700 °C. A comparison with theoretical models describing the growth of coherently strained and plastically relaxed islands is given to describe the observations. The mean diameter of coherently strained islands is found to be 170 nm over a wide range of temperature, whereas plastically relaxed islands grow up to diameters 〉500 nm. The aspect ratio turns out to be independent of the presence of dislocations. For the sample grown at 700 °C three size regimes could be observed, whereas the sample grown at the lowest temperature exhibits no island formation. At 550 °C islands with an average diameter of 33 nm and a low aspect ratio were observed; these could prove to be interesting in applications using quantum confinement effects. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.119553
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