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  • 1
    Digitale Medien
    Digitale Medien
    Construction of higher-moment terms in the hydrodynamic electron-transport model (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 6197-6207 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.355189
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  • 2
    Digitale Medien
    Digitale Medien
    An improved ionized-impurity scattering model for Monte Carlo simulations (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 1475-1482 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.349560
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  • 3
    Digitale Medien
    Digitale Medien
    Monte Carlo calculation of strained and unstrained electron mobilities in Si1−xGex using an improved ionized-impurity model (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 1483-1488 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.349561
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  • 4
    Digitale Medien
    Digitale Medien
    S-bend loss in disorder-delineated GaAs heterostructure laser waveguides with native and blue shifted active regions (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 741-744 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.103431
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  • 5
    Digitale Medien
    Digitale Medien
    Microstructure, heat treatment, and oxidation study of porous silicon formed on moderately doped p-type silicon (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 492-496 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.364107
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  • 6
    Digitale Medien
    Digitale Medien
    Electroabsorption in single quantum well GaAs laser structures (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 1716-1718 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.101291
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  • 7
    Digitale Medien
    Digitale Medien
    Impact ionization coefficient and energy distribution function at high fields in semiconductors (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 4279-4286 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.343313
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  • 8
    Digitale Medien
    Digitale Medien
    Iso-electronic impurity-induced disordering: AlxGa1−xAs-GaAs/In (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 2880-2882 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Data are presented on the disordering of an AlxGa1−xAs-GaAs laser structure using indium solid sources. Using separate and co-diffusion of silicon and indium from thin-film sources, indium was inferred to have a higher diffusion coefficient than silicon, and to result in a similar degree of impurity-induced disordering. The degree of index guiding was tested by excess-loss measurements in single-mode raised-cosine s-bends. In particular, structures patterned by SiO2/In disordering had excess losses similar to those patterned with SiO2. A 260 μm transition length for 3 dB loss was measured for 1-μm-wide guides with 100 μm guide offsets, which corresponds to a lateral index of refraction difference of ≈0.8–1.0%. There was no evidence for increased linear loss due to the presence of a dilute InGaAs alloy at the measurement wavelength of 870 nm.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.105840
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  • 9
    Digitale Medien
    Digitale Medien
    Erratum: "Giant magnetoresistance of the La1−xAgxMnO3 polycrystalline inhomogeneous granular system" [Appl. Phys. Lett. 77, 723 (2000)] (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 1560-1560 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1311403
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  • 10
    Digitale Medien
    Digitale Medien
    Giant magnetoresistance of the La1−xAgxMnO3 polycrystalline inhomogeneous granular system (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 723-725 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A series of bulk polycrystalline La1−xAgxMnO3 samples with x ranging nominally from 0 to 0.5 were prepared by conventional solid-state reaction processing in air. X-ray diffraction patterns show that the samples contain a single perovskite phase when x≤0.25, and are composed of two phases (a magnetic perovskite phase and a nonmagnetic Ag-rich phase) for x〉0.25. It is found that, in this series of polycrystalline samples, maximum magnetoresistance occurs for x=0.30, i.e., for a composite of the two phases whose magnetoresistance ratio is about 25.5% at room temperature. The enhancement of the magnetoresistance effect in such an inhomogeneous granular system can be attributed to the spin-dependent scattering of electrons at the interface of the two phases. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.127098
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