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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},
}
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