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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 5676-5681 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A self-assembled Ge/Si quantum dot interlevel infrared photodetector operating at room temperature and at normal incidence is demonstrated. The spectral response exhibits two peaks in the 58–82 and 132–147 meV energy regions with full width at half maximum linewidths as narrow as 25 meV. The two photocurrent maxima are ascribed to transitions from the hole ground state to the excited states in the dots. The peak detectivity and responsive quantum efficiency are 1.7×108 cm Hz1/2/W and 0.1% for the transition from the ground state to the first excited state and 7×107 cm Hz1/2/W and 0.08% for the transition from the ground state to the second excited state. At large dc bias, a redshift in the transition energies is observed. We argue that the resonance shifts are due to suppression of the depolarization field effect, representing the experimental manifestation of dynamic screening associated with collective electron–electron interaction in the dots. © 2001 American Institute of Physics.
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  • 2
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Room-temperature infrared photoconductivity in a single layer of Ge self-assembled quantum dots incorporated into silicon p-i-n diode is reported. An in-plane polarized photocurrent response with two bias controlled maxima at 2.9 μm and at 1.7 μm wavelength has been observed. The two kinds of absorption driven by reverse bias in opposite ways are ascribed to the intraband hole bound-to-continuum transition and to the interband excitonic transition. © 1999 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 81 (2002), S. 499-501 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Resonant tunneling diodes were implemented on Ge quantum dots fabricated using Stranski–Krastanov growth mode on CaF2 matrix, lattice matched to Si(111) substrates. The negative differential conductance and conductance oscillations due to hole resonant tunneling through the zero-dimensional states of Ge quantum dots are clearly observed at room temperature. From the period of conductance oscillations, the energy separations between the states of the quantum dots with different sizes are estimated to be 40–50 meV (i.e., 〉kT=26 meV at T=300 K). © 2002 American Institute of Physics.
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  • 4
    ISSN: 1063-7826
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The generally accepted notions about the formation mechanisms for germanium islands with nanometer-scale sizes in a Ge-on-Si system are reviewed on the basis of analysis of recent publications. The presence of elastic strains in the epilayers and in the three-dimensional Ge islands on Si is a key factor that not only initiates a morphological transition from a planar film to an island-containing film (the Stranski-Krastanov mechanism) but also influences the subsequent stages of the islands’ evolution, including their shape, size, and spatial distribution. In many cases, this factor modifies appreciably the classical mechanisms of phase-formation and their sequence up to the quasi-equilibrium coexistence of three-dimensional Ge nanoislands at the surface of the Si substrate. The methods for improving the degree of the ordering of nanoislands to attain the smallest possible sizes and large density of areal distribution of these islands are discussed. The published data on optical absorption in the multilayered Ge-Si systems with quantum dots are considered; these data are indicative of an anomalously large cross section of intraband absorption, which makes this class of nanostructures promising for the development of photodetectors of the infrared region of the spectrum. The results of original studies of electrical and optical properties of heterostructures that involve Ge quantum dots and are synthesized by molecular-beam epitaxy on the Si substrates are reported.
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  • 5
    ISSN: 1063-7834
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Electron spin resonance has been used to study the depth distribution of point defects in Si samples bombarded by N5+ (E=16 MeV) and Si5+ (E=26.8 MeV) ions at 175 and 300 K in the dose range (4–8)×1015 cm−2. It was established that unlike the implantation of moderate-energy Si ions (E ∼ 100 keV), the depth distributions of planar tetravacancies in samples bombarded by ions at 300 K under these conditions have two maxima. The experimental results indicate that the tetravacancy density maximum closer to the surface is formed as a result of secondary defect formation processes. No continuous amorphous layer was observed in the bulk of any of the Si samples. This experimental observation is evidence of defect annealing which takes place when high-energy ions are implanted in Si.
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  • 6
    ISSN: 1090-6487
    Keywords: 81.15.Hi ; 73.20.Dx ; 68.65.+g
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The characteristic features of electronic spectra in Ge/Si (100) heterostructures obtained by molecular-beam epitaxy are investigated by capacitance spectroscopy. It is observed that the self-organization of a Ge film into an island film when the effective germanium thickness exceeds six monolayers is accompanied by the appearance of hole bound states, which can be attributed to size quantization and the Coulomb interaction of carriers in the array of Ge quantum dots.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    JETP letters 65 (1997), S. 354-358 
    ISSN: 1090-6487
    Keywords: 71.23.Cq ; 71.30.+h
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A metal-insulator transition (MIT) induced by a change in the impurity Mn concentration in a material with topological disorder — amorphous Si1−c Mnc — is investigated. It is found that near the critical point the localization radius, permittivity, and conductivity vary according to a power law in accordance with the scaling theory of localization. The critical exponents are determined. It is concluded that the basic mechanisms of the MIT in disordered systems do not depend on the type of disorder and are universal.
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  • 8
    ISSN: 1090-6487
    Keywords: 73.20.Mf ; 73.50.Pz
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract It was found that irradiating an array of Ge nanoclusters in n-Si with light that induced interband transitions gave rise to negative photoconductivity. This result was explained by localization of equilibrium electrons at the Si/Ge interface in the potential of the nonequilibrium holes trapped on deep states in Ge islands.
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  • 9
    ISSN: 1090-6487
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The conductance along an island layer of Ge quantum dots buried in silicon was investigated. The sizes of the islands varied in the range D ≈ 12−19 nm. It was found that the charge transport is characterized by two activation energies. The first one is associated with the thermal emission of holes from Ge quantum wells into the valence band of Si. The second one is due to the tunneling of holes between islands under Coulomb blockade conditions and is determined by the electrostatic charging energy of a quantum dot.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    JETP letters 67 (1998), S. 539-544 
    ISSN: 1090-6487
    Keywords: 81.15.Hi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The mechanism of silicon epitaxy on porous Si(111) layers is investigated by the Monte Carlo method. The Gilmer model of adatom diffusion extended to the case of arbitrary surface morphology is used. Vacancies and pendants of atoms are allowed in the generalized model, the activation energy of a diffusion hop depends on the state of the neighboring positions in the first and second coordination spheres, and neighbors located outside the growing elementary layer are also taken into account. It is shown that in this model epitaxy occurs by the formation of metastable nucleation centers at the edges of pores, followed by growth of the nucleation centers along the perimeter and the formation of a thin, continuous pendant layer. Three-dimensional images of surface layers at different stages of epitaxy were obtained. The dependence of the kinetics of the epitaxy process on the amount of deposited silicon is determined for different substrate porosities.
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