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  • 1
    Electronic Resource
    Electronic Resource
    Strain modification in thin Si1−x−yGexCy alloys on (100) Si for formation of high density and uniformly sized quantum dots (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 578-582 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effects of alloying C with Ge and Si and varying the C/Ge ratio during the growth of very thin layers of the ternary alloy SiGeC grown on Si (100) substrates and the resulting strain modification on self-assembled and self-organized quantum dots are examined. During coherent islanded growth, where dislocations are not formed yet to relieve the strain, higher strain energy produced by greater lattice mismatch acts to reduce the island size, increase the density of islands, and significantly narrow the distribution of island sizes to nearly uniformly sized quantum dots. Strain energy can also control the critical thickness for dislocation generation within the three-dimensional islands, which then limits the maximum height which coherent islands can achieve. After the islands relax by misfit dislocations, the island sizes increase and the island size distribution becomes broader with the increase of misfit and strain. The optimal growth for a high density of uniform coherent islands occurred for the Si0.49Ge0.48C0.03 alloy composition grown on (100) Si, at a growth temperature of 600 °C, with an average thickness of 5 nm, resulting in a narrow size distribution (about 42 nm diameter) and high density (about 2×1010 dots/cm2) of quantum dots. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369492
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  • 2
    Electronic Resource
    Electronic Resource
    Precipitation of β-SiC in Si1−yCy alloys (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 4631-4633 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The infrared modes of annealed Si1−yCy alloys were studied experimentally and theoretically. The alloys were grown on Si(100) substrates by solid-source molecular beam epitaxy and were characterized by Fourier transform infrared spectroscopy. At annealing temperatures above 850 °C, the localized vibrational mode of substitutional C around 605 cm−1 diminished in intensity while another mode due to incoherent silicon carbide precipitates appeared at 810 cm−1. For lower processing temperatures, a peak around 725 cm−1 has been tentatively attributed to a C-rich phase, which is a precursor to SiC precipitation. Theoretical calculations based on the anharmonic Keating model predict that small (1 nm) 3C–SiC coherent precipitates may actually produce a mode at 725 cm−1. This mode occurs if the bonds gradually vary in length between the C-rich region and the host lattice. On the other hand, if the bonds are abruptly distorted at the edges of the precipitate, it becomes elastically isolated from the host lattice, and the 810 cm−1 mode appears. This study yields a picture of the thermal stability of dilute SiC alloys, which is important for the high-temperature processing steps necessary for device applications. Moreover, the coherent precipitation may provide a controllable way to form self-assembled 3C–SiC quantum dots into silicon germanium carbon alloys. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368703
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  • 3
    Electronic Resource
    Electronic Resource
    Photoluminescence investigation of phononless radiative recombination and thermal-stability of germanium hut clusters on silicon(001) (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 2261-2263 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Intense photoluminescence (PL) originating from single layers of germanium hut clusters grown on silicon (001) is investigated using PL spectroscopy. We propose that the luminescence originates from phononless recombination within a spatially indirect, type-II neighboring confinement structure. Enhanced no-phonon (NP) luminescence is attributed to exciton localization at the Ge/Si interfaces. The PL intensity is sensitive to the growth temperature during interface formation, as well as to post-growth thermal annealing, illustrating the influence of atomic-level Si–Ge intermixing on exciton localization and NP enhancement. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1405148
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  • 4
    Electronic Resource
    Electronic Resource
    Photoluminescence of ultrasmall Ge quantum dots grown by molecular-beam epitaxy at low temperatures (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 1279-1281 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low-temperature epitaxial growth of Si–Ge heterostructures opens possibilities for synthesizing very small and abrupt low-dimensional structures due to the low adatom surface mobilities. We present photoluminescence from Ge quantum structures grown by molecular-beam epitaxy at low temperatures which reveals a transition from two-dimensional to three-dimensional growth. Phononless radiative recombination is observed from 〈105〉 faceted Ge quantum dots with height of approximately 0.9 nm and lateral width of 9 nm. Postgrowth annealing reveals a systematic blueshift of the Ge quantum dot's luminescence and a reduction in nonradiative recombination channels. With increasing annealing temperatures Si–Ge intermixing smears out the three-dimensional carrier localization around the dot. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1430508
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  • 5
    Electronic Resource
    Electronic Resource
    Dielectric response of thick low dislocation-density Ge epilayers grown on (001) Si (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 4084-4086 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Spectroscopic ellipsometry was used to measure the dielectric functions of epitaxial and bulk Ge at photon energies from 1.5 to 5.2 eV. The epitaxial Ge was grown at 400 °C by molecular beam epitaxy on (001) Si substrates. The optical response and the interband critical-point parameters of Ge on Si were found to be indistinguishable from that of bulk single crystal Ge, indicating high optical quality. Dislocation density measurements using an iodine etch verified low surface defect densities. We conclude that epitaxial Ge grown on Si at relatively low temperatures is suitable for optical device applications. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117826
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  • 6
    Electronic Resource
    Electronic Resource
    1.3 μm photoresponsivity in Si-based Ge1−xCx photodiodes (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 1860-1862 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ge1−xCx/Si heterostructure photodiodes with nominal carbon percentages (0≤x≤0.02), which exceed the solubility limit, were grown by solid source molecular beam epitaxy on n-type (100) Si substrates. The p-Ge1−xCx/n-Si photodiodes were fabricated and tested. The p-Ge1−xCx/n-Si junction exhibits diode rectification with a reverse saturation current of about 10 pA/μm2 at −1 V and high reverse breakdown voltage, up to −80 V. A significant reduction in diode reverse leakage current was observed by adding C to Ge, but these effects saturated with more C. Photoresponsivity was observed from these Si-based p-Ge1−xCx/n-Si photodiodes at a wavelength of ≥1.3 μm, compatible with fiber optic wavelengths. External quantum efficiency of these thin surface-normal photodetectors was measured up to 2.2%, which decreased as the carbon percentage was increased. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121207
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  • 7
    Electronic Resource
    Electronic Resource
    Thermally oxidized AlN thin films for device insulators (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 2732-2734 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The structural, optical, and electronic properties of an insulating material prepared by the thermal oxidation of AlN thin films on Si have been studied by a number of different experimental techniques. The thermal oxidation at 1100 °C of reactively sputtered AlN films on Si wafers was found to result in the formation of an oxide with a relative Al to O concentration near Al2O3 with small amounts of incorporated N. The structure of the AlO:N oxide could be varied between amorphous and polycrystalline, depending on the preparation conditions, and the oxide surface was found to be approximately three time smoother than the as-sputtered AlN films. Metal–oxide–silicon capacitors had an oxide charge density of about 1011 cm−2, capacitance–voltage characteristics similar to pure SiO2, and a dielectric constant of 12.4. Infrared measurements yielded a refractive index of 3.9. These results indicate that thermally oxidized AlN films show promise as insulating structures for many integrated circuit applications, particularly for the case of III–V and group III–nitride based semiconductors. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118980
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  • 8
    Electronic Resource
    Electronic Resource
    Room temperature operation of epitaxially grown Si/Si0.5Ge0.5/Si resonant interband tunneling diodes (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 2191-2193 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Resonant interband tunneling diodes on silicon substrates are demonstrated using a Si/Si0.5Ge0.5/Si heterostructure grown by low temperature molecular beam epitaxy which utilized both a central intrinsic spacer and δ-doped injectors. A low substrate temperature of 370 °C was used during growth to ensure a high level of dopant incorporation. A B δ-doping spike lowered the barrier for holes to populate the quantum well at the valence band discontinuity, and an Sb δ-doping reduces the doping requirement of the n-type bulk Si by producing a deep n+ well. Samples studied from the as-grown wafers showed no evidence of negative differential resistance (NDR). The effect of postgrowth rapid thermal annealing temperature was studied on tunnel diode properties. Samples which underwent heat treatment at 700 and 800 °C for 1 min, in contrast, exhibited NDR behavior. The peak-to-valley current ratio (PVCR) and peak current density of the tunnel diodes were found to depend strongly on δ-doping placement and on the annealing conditions. PVCRs ranging up to 1.54 were measured at a peak current density of 3.2 kA/cm2. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122419
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  • 9
    Electronic Resource
    Electronic Resource
    Carbon incorporation in Si1−yCy alloys grown by molecular beam epitaxy using a single silicon–graphite source (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 833-835 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Pseudomorphic Si1−yCy alloys on silicon (100) were grown by molecular beam epitaxy using a single effusion source of silicon contained in a graphite crucible, producing carbon concentrations of y=0.008. The behavior of carbon incorporation using this source was studied as a function of growth temperature using x-ray diffraction and infrared spectroscopy, and was compared to previous studies, where Si1−yCy was grown from separate silicon and graphite sources. An increased energy barrier for the surface diffusion of carbon was observed using the single silicon–graphite source. An infrared absorption mode near 725 cm−1, observed for growth temperatures up to 700 °C, was attributed to a transitional phase between the loss of substitutional carbon and the formation of silicon carbide precipitates. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120908
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  • 10
    Electronic Resource
    Electronic Resource
    The effect of composition on the thermal stability of Si1−x−yGexCy/Si heterostructures (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 1972-1974 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The thermal stability of molecular beam epitaxy grown Si1−x−yGexCy/Si heterostructures (0≤x〈0.30, y∼0.008) was studied using infrared absorption spectroscopy. The local vibrational mode of C in Si and Si1−x−yGex was used to quantify the loss of C atoms from substitutional sites with high temperature annealing. The activation energy (Ea=4.9 eV) for the loss of substitutional C achieved a maximum for the strain compensated alloy (x∼0.1). An additional increase of Ge content resulted in a rapid decrease in Ea, which was found to be 3.4 eV for x∼0.27. The nonmonotonic behavior of Ea on Ge content is explained by the effect of the interface strain between the epitaxial layer and Si substrate. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121238
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