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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 492-496 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A porous Si (PS) layer with a spongy microstructure on top of a dendritic microstructure was fabricated on a moderately doped p-type Si wafer using a two-step anodization process. This illustrates that in addition to substrate doping, anodization current density also has an effect on the porous Si microstructure. A preoxidation heat treatment of the spongy-type porous Si was found to change the porous structure significantly, making it more difficult to fully oxidize the layer at low temperatures. However, dendritic porous Si can better withstand the heat treatment without suffering noticeable changes in structure. X-ray photoelectron spectroscopy, infrared spectroscopy, and electrical breakdown tests were used to analyze the oxidized porous Si samples. The oxidation process and the resultant oxide were found to depend on several factors, including the porosity, the microstructure itself (e.g., spongy or dendritic-type), and the heat treatment history prior to oxidation. With similar porosity, dendritic PS is easier to oxidize compared to spongy PS. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 982-983 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An alternative masking method for high-voltage ion implantation masking of compound semiconductors which incorporates an additional AlGaAs layer between a Pb/Cr/Au metal mask and the sample to be implanted is described. Following patterning by conventional techniques and implantation, the AlGaAs layer is selectively etched to remove the metal mask without damaging the underlying epitaxial structure.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6197-6207 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A critical step in the development of all hydrodynamic transport models (HTMs), derived from moments of the Boltzmann transport equation, is the introduction of accurate closure relations to terminate the resulting infinite set of macroscopic equations. In general, there are a number of resulting integral terms that are highly dependent on the form of the true electron distribution function. The so-called heat flux term is one very important higher-moment term that requires attention. Methods for the accurate construction of an improved heat-flux model are presented. In this construction, a higher-moments approach is combined with a unique definition of electron temperature (i.e., based upon an ansatz distribution) to investigate the effects of conduction-band nonparabolicity and distributional asymmetry. The Monte Carlo method has been used to evaluate the resulting model closures and to study microscopic electron dynamics. These investigations have identified an important relationship between a particular symmetric (i.e., thermal) component of the electron distribution function and the heat flow vector. This knowledge is important because all the parameters in the HTM must be closed (i.e., related to each other through a common set of system variables) before the technique can be accurately applied to the study of electron transport in semiconductor devices.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 1475-1482 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An improved Monte Carlo model for ionized-impurity scattering is developed and used to calculate majority- and minority-electron mobilities in silicon. The model includes scattering cross sections derived from phase-shift analysis, implementation of the Friedel sum rule, and a simple phenomenological model for multiple-potential scattering. This model provides a very good fit to experiment using a single adjustable parameter. Electron mobilities in n- and p-type Si are calculated and fit to experimental data at 300 and 77 K. Experimental results for Si of μn(NA)/μn(ND) ≈ 2 at 300 K are reproduced and a value of 3 〈 μn(NA)/μn(ND) 〈 4 is predicted at 77 K.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7103-7103 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: (BiDy)Fe5O12 films in the amorphous state were made by rf magnetron sputtering from a sintered Bi2DyFe5O12 ceramic target onto quartz substrates and confirmed by x-ray diffraction. The films were annealed at different temperatures ranging from 500 to 800 °C for 1 h in air. The crystallization temperature was about 650 °C, as measured by DTA method. Magnetization M versus temperature relation of well crystallized films showed both a compensation temperature Tcomp (80 K) and Curie temperature TC (563 K). The M-T curve from 1.5 to 600 K of amorphous film showed no definite TC or Tcomp; M measured in a field of 20 kOe decreased monotonously. The Faraday rotation (500–700 nm) of amorphous films was small. The M and Faraday rotation (633 nm) increased rapidly at the crystallization temperature. The Bi ion induced peak (550 nm) in the Faraday spectra got higher with the increasing annealing temperature and was up to 9.14 degree/μm. The Faraday spectra of films annealed at 650 °C for different times showed that the films were well crystallized after annealing for 10 min. The optical absorption of the films in the visible region varied little during the transformation from amorphous to polycrystalline.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 1483-1488 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An improved Monte Carlo (MC) model for ionized impurity scattering developed in a previous work [L. E. Kay and T.-W. Tang, J. Appl. Phys. 70 1475 (1991)] is used to perform a comprehensive study of majority- and minority-electron mobilities in the Si1−xGex material system for both strained and unstrained cases. This investigation includes calculation of low-field mobilities for wide ranges of doping and Ge mole fraction at both 300 and 77 K as well as high-field studies. A significant improvement in mobility (up to 50%) is observed for transport perpendicular to the growth plane in strained Si1−xGex as compared to the unstrained case. The magnitude of the improvement is dependent on doping (both concentration and type) and germanium content, and is somewhat larger at 77 K. High-field MC simulations show that some strained-mobility enhancement remains even at an electric field of 100 kV/cm. These studies also suggest there is a temperature-dependent Ge content for which mobility is maximized at higher dopings.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 113-115 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The transformation of nonplanar periodic laser array modes from weakly locked out-of-phase to locked in-phase operation is investigated. A comparison study of near-field and far-field patterns is made for devices with differing mesa widths and heights. Data are presented which show that the mesa height and width can be adjusted to force in-phase operation. An array of 19 elements shows an essentially single-lobed far-field pattern centered at 0° with full width at half maximum of 1.6°, to output powers of more than 500 mW/uncoated facet.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 4279-4286 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Impact ionization coefficients in semiconductors are numerically calculated following Keldysh's method [Sov. Phys. JETP 21, 1135 (1965)]. This requires deriving expressions for an energy-dependent mean free path l(ε) and an energy-dependent impact ionization scattering rate rii(ε). In the derivation of rii(ε), a nonparabolic ε-k relation as well as a smooth transition from the phonon-assisted impact ionization to the phononless impact ionization are considered. Numerically calculated impact ionization coefficients for electrons and holes in Ge, Si, and GaAs agree very well with experimental data. The calculated Keldysh energy distribution function is also compared with the standard Maxwellian distribution. The average mean free path l¯, which is a function of the electric field, has values within the range often quoted in the literature.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1716-1718 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electric field dependent spectral properties of a GaAs graded barrier quantum well heterostructure laser are measured for the first time. Data are presented which show that the electroabsorption below the band gap is due to states in the confinement layers which are perturbed by the quantum well under high field conditions. This effect, which is intermediary between the quantum confined Stark effect and bulk Franz–Keldysh effect, should be present in all quantum well systems with shallow wells in short, high field depletion regions.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The routing ability of waveguide S-bend structures patterned by SiO2 impurity induced layer disordering of a single GaAs quantum well graded barrier laser structure is investigated. For a raised-cosine bend with 100 μm offset guides, the measured transition length for 3 dB loss was less than 300 μm for near single mode guides of 1 μm width. In addition, vacancy-induced disordering of the native quantum well region is investigated and is shown to increase the band gap to a point where the material is low loss for radiation generated by the laser. The 3 dB length for these blue shifted cores actually decreased to about 230 μm, a fact attributed to reduced mode conversion.
    Type of Medium: Electronic Resource
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