Quantum Transport in Advanced Field-Effect Transistors for Ongoing and Future Electronics

• Author / Creator

  Wong, Michael C

• The electronics industry has already moved to non-conventional transistor geometries in order to overcome the limitations associated with aggressive transistor scaling. Fin field-effect transistors (FinFETs) enable further scaling by giving the gate better electrostatic control over the channel, which combats adverse short-channel effects. However, FinFETs are also now approaching the scaling limit. Two-dimensional field-effect transistors (2DFETs) have therefore recently garnered interest as a replacement for FinFETs. These 2DFETs are an exciting area of research, as there exists a wealth of possible channel materials with widely varying properties, offering a vast array of options for transistor design.
  Due to the non-conventional geometries of advanced transistors and the small dimensions involved, transistor operation is heavily impacted by quantum-mechanical effects, an issue that renders classical modeling methods ineffective. In this work, we employ quantum transport simulation, which natively and accurately captures these quantum-mechanical effects, in order to model and predict the characteristics of FinFETs and 2DFETs.
  In the first stage of work, we consider line-edge roughness (LER) in FinFETs, a nonideality that has already been shown to be very important in aggressively scaled FinFETs. We examine the impact of both short-wavelength and long-wavelength LER on FinFET operation, identifying which is more detrimental, and suggesting mechanisms by which the influence of LER can be mitigated.
  In the second stage, we consider wave function deformation scattering (WDS), another nonideality that can be significant in ultrascaled FinFETs, especially in the presence of LER. We show that the impact of WDS can be predicted by considering the carrier effective masses in the channel, and that WDS is the most impactful in materials with low effective mass in the transport direction and high effective mass in the confinement direction.
  In the third stage, we consider tin (IV) disulfide and hafnium disulfide, both two-dimensional materials that have been considered recently as channel materials for 2DFETs. We examine the on-current and unity-current-gain frequency of 2DFETs using these materials and provide a physical explanation for the lack of anisotropy in transistor characteristics despite the presence of anisotropic conduction band valleys in the electronic structure.
  Overall, this work thus enhances our understanding of subtle quantum transport phenomena that dictate FinFET and 2DFET behavior, which is of critical importance for the continued advancement of electronics in both the near- and long-term future.

• Subjects / Keywords

  • finfets
  • quantum transport
  • 2dfets
  • transistor

• Graduation date

  Fall 2019

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-40vv-vz50

• License

  Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.