Abstract

Tunnel field-effect transistors (TFETs) have long been considered as a replacement technology for metal-oxide-semiconductor field-effect transistors in low power digital applications due to their low OFF-current and small subthreshold swing. These benefits are somewhat neutralized by the low ON-current exhibited by TFETs fabricated with large bandgap semiconductors such as silicon. To offset this drawback, different material systems can be used, with material optimization required for the channel material, the gate stack, and their corresponding geometries. This study considers the novel idea of using 2-dimensional (2D) semiconductors for the channel material in TFETs, and the potential effects of such a channel on the physics of the resulting device. After this theoretical discussion of TFETs, the simulation requirements of such a device are introduced as well as the two quantum simulation systems of choice: the Vienna Ab initio Simulation Package (VASP 5.4) as offered by Materials Design and NanoHUB's NEMO5. Topics examined with simulation theory in mind include the density functional theorem (DFT) and convergence criteria. Previously fabricated Esaki diodes from Pawlik et al. are simulated using NEMO5 and the necessity of bowing application to the tight-binding parameters is shown. Tables clarifying the tight-binding parameters of InGaAs from the NEMO5 all.mat file and their associated bowing parameters are included. The simulations performed with the bowing parameters included are shown to match the experimental data almost exactly. Initial VASP 5.4 simulations for GaAs and InAs are shown and the practicality of DFT using the generalized gradient approximation (GGA), HSE06 with GGA, and Hartree-Fock methods is discussed; HSE06 with GGA is shown to produce simulations closest to reality, though there is a signicant computation time trade-off. A designed experiment varying the lattice constants of MoS2 and WTe2 is performed and included as an example of the simulation systems capabilities. A plot of VASP 5.4 and NEMO5 MoS2 bandstructure results is also included.

Library of Congress Subject Headings

Tunnel diodes--Computer simulation; Tunnel field-effect transistors--Computer simulation; Tunnel field-effect transistors--Materials

Publication Date

7-19-2018

Document Type

Thesis

Student Type

Graduate

Degree Name

Microelectronic Engineering (MS)

Department, Program, or Center

Microelectronic Engineering (KGCOE)

Advisor

Sean L. Rommel

Advisor/Committee Member

James E. Moon

Advisor/Committee Member

Santosh Kurinec

Campus

RIT – Main Campus

Plan Codes

MCEE-MS

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