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@PHDTHESIS{Noei:794157,
      author       = {Noei, Maziar},
      othercontributors = {Jungemann, Christoph and Meinerzhagen, Bernd},
      title        = {{D}eterministic simulation of junctionless nanowire field
                      effect transistors},
      school       = {Rheinisch-Westfälische Technische Hochschule Aachen},
      type         = {Dissertation},
      address      = {Aachen},
      reportid     = {RWTH-2020-07441},
      pages        = {1 Online-Ressource (148 Seiten) : Illustrationen,
                      Diagramme},
      year         = {2020},
      note         = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
                      University; Dissertation, Rheinisch-Westfälische Technische
                      Hochschule Aachen, 2020},
      abstract     = {As the feature lengths of the field-effect transistors
                      (FETs) are scaled down to the deca-nanometer range, the
                      commonly used macroscopic approaches such as drift-diffusion
                      and hydrodynamic models lose their validity and a detailed
                      description of the microscopic behavior of charge carriers
                      becomes essential for device simulation. In this work, a
                      fully self-consistent and deterministic solver for the
                      system of Poisson, Schrödinger, and Boltzmann equations
                      tailored to the specific case of gate-all-around
                      junctionless nanowire FETs is developed. The simulation
                      framework employs various numerical techniques such as the
                      H-transformation and an even/odd decomposition of the
                      distribution function on a staggered grid for stabilization
                      of the Boltzmann equation (BE), and the equations are solved
                      with the Newton-Raphson approach which demonstrates
                      quadratic convergence within just a few iterations.
                      Different inter- and intra-valley scattering mechanisms,
                      suitable boundary conditions, and quantization effects are
                      included, and the solver is shown to be robust and stable
                      even in the deep subthreshold region. In addition to the
                      stationary simulations, small signal analysis is carried out
                      under the sinusoidal steady state condition and important
                      figures of merit such as the cut-off frequency, maximum
                      oscillation frequency, and Rollet stability factor are
                      obtained and discussed. Moreover, the Langevin-source
                      approach is used for self-consistent calculation of noise,
                      resulting in the first deterministic BE solver for noise
                      analysis of nanowire FETs. Quantities such as the power
                      spectral densities of terminal currents, the drain and gate
                      excess noise factors, cross-correlation, and the noise
                      suppression factors are presented and compared for different
                      gate lengths. In the second part of this work, an
                      alternative approach based on the characteristic curves and
                      matrix exponentials is developed for the discretization of
                      the BE, which is also applicable to the ballistic transport
                      and does not sufferfrom the numerical deficiencies of
                      H-transformation in 1D phase space. The results of the
                      quasi-ballistic simulations are presented and compared to
                      those of the moments equations obtained from the projection
                      of the BE onto Hermite polynomials. It is shown that the
                      predominantly ballistic phenomena cannot be treated with
                      systems of moments equations and simplified boundary
                      conditions. The failure of moments model in describing the
                      ballistic modes of transport has important implications for
                      the existence of Dyakonov-Shur terahertz instabilities in
                      high mobility 1D devices.},
      cin          = {611410},
      ddc          = {621.3},
      cid          = {$I:(DE-82)611410_20140620$},
      typ          = {PUB:(DE-HGF)11},
      doi          = {10.18154/RWTH-2020-07441},
      url          = {https://publications.rwth-aachen.de/record/794157},
}