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@PHDTHESIS{Sandow:156341,
      author       = {Sandow, Christian Philipp},
      title        = {{M}odeling, fabrication and characterization of silicon
                      tunnel field-effect transistors},
      volume       = {15},
      school       = {RWTH Aachen},
      type         = {Dr.},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2014-05105},
      isbn         = {978-3-89336-675-0},
      series       = {Schriften des Forschungszentrums Jülich . Reihe
                      Information / information},
      pages        = {XIII, 112 S. : Ill., graph. Darst.},
      year         = {2010},
      note         = {RWTH Aachen, Diss., 2010},
      abstract     = {Over the last decades, the continuous down-scaling of
                      metal-oxide-semiconductor field-effect transistors (MOSFETs)
                      enabled faster and more complex chips while at the same time
                      the space and power-consumption was kept under control.
                      However, in the future, the further reduction of the power
                      consumption per unit area will be restricted by a
                      fundamental limit of the inverse subthreshold swing of
                      MOSFETs, which relates its on/off-current-ratio to the
                      operation voltage. Since logic devices operate at a given
                      on/off-currentratio, the limited subthreshold swing will
                      prevent further reduction of the operation voltage, which is
                      the main parameter to reduce the power consumption. In this
                      thesis, the Tunnel-FET (TFET) is studied as an alternative
                      switching device which could overcome the physical limit of
                      the subthreshold slope in MOSFETs. After introducing the
                      working principle of the TFET, device parameters are studied
                      extensively in quantum simulations based on the
                      non-equilibrium- Green’s-function method. It is found that
                      the performance of a nanowire device geometry is superior to
                      that of planar structures and that the gate dielectric
                      should be as thin as possible. Moreover, the impact of
                      doping concentration on the switching behavior is
                      investigated. For very large doping concentrations, the
                      subthreshold swing is expected to deteriorate while smaller
                      doping concentrations lead to reduced oncurrents. Therefore,
                      the doping concentrations need to be tailored to a specific
                      application. Finally, TFETs with different substrate
                      materials are simulated and the influence of bandgap and
                      effective masses is illustrated. A small bandgap improves
                      band-to-band tunneling currents, therefore, the on-currents
                      of the TFET increase. However, due to the ambipolar behavior
                      of the TFET, the off-currents increase as well. Therefore,
                      an optimal TFET is proposed, which is a heterostructure
                      nanowire that utilizes a small bandgap material at the
                      source/channel-junction and a large bandgap material at the
                      drain/channel-junction. The extensive simulations are
                      complemented by a study on different experimental
                      realizations of the TFET: As a first step, planar silicon
                      TFETs were fabricated on ultra-thin-body
                      silicon-on-insulator substrates. The resulting TFETs exhibit
                      minimal inverse subthreshold slopes of 325 mV/dec and
                      on-currents of the order of 10$^{-2}$ μA/μm. Since these
                      results are inferior to MOSFET performance, optimizations of
                      the doping concentration and gate dielectric thickness are
                      investigated and both parameters are found to impact the
                      performance as predicted by the simulations. Furthermore,
                      the lateral steepness of the source doping profile is
                      identified as an important parameter, which limits the
                      switching slope. To benefit from the improved electrostatics
                      of nanowires, in a second step, silicon nanowire array TFETs
                      with widths of < 20 nm were fabricated using a top-down
                      approach. In order to optimize the slope of the doping
                      profile, for the first time laser annealing was employed for
                      dopant activation in TFETs. To find the optimum annealing
                      conditions, the impact of different laser energies in
                      combination with a thermal postanneal treatment on the TFET
                      performance is studied. The electrical characterization of
                      the nanowire TFETs shows an improvement of the subthreshold
                      swing by about 10\% and of the on-currents by one order of
                      magnitude when compared to the planar TFETs. To deepen the
                      understanding of TFET operation, low temperature
                      measurements have been performed and band-to-band tunneling
                      is found to be the dominant conduction method. Moreover, for
                      the first time possible parasitic recombination mechanisms
                      are identified in a TFET which might limit the switching
                      slope in silicon. Since small-band gap heterostructure
                      nanowires might offer largely improved tunneling
                      probabilities, in this thesis, a first experimental
                      realization of InSb nanowire MOSFETs is presented. As the
                      bandgap is the most important property for TFET
                      applications, it is carefully extracted from the electrical
                      characteristics and it is found to match the value known
                      from bulk InSb very well. In summary, this thesis presents
                      quantum simulations and two experimental realizations of
                      TFETs in silicon are studied in detail. Variations of device
                      parameters show a path for further optimizations of silicon
                      TFETs. As a first step beyond silicon, InSb nanowire MOSFETs
                      are fabricated successfully for the first time and the
                      potential of InSb for TFET operation is discussed.},
      keywords     = {Dissertation (GND)},
      cin          = {PGI-9},
      ddc          = {621.3},
      cid          = {I:(DE-Juel1)PGI-9-20110106},
      pnm          = {421 - Frontiers of charge based Electronics (POF2-421)},
      pid          = {G:(DE-HGF)POF2-421},
      typ          = {PUB:(DE-HGF)11},
      urn          = {urn:nbn:de:hbz:82-opus-34530},
      url          = {https://juser.fz-juelich.de/record/156341},
}