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First-Principles Calculations on the...

Mengle, Kelsey.

First-Principles Calculations on the Electronic, Optical, and Vibrational Properties of Ultrawide-Band-Gap Semiconductor Materials.

Record Type:	Electronic resources : Monograph/item
Title/Author:	First-Principles Calculations on the Electronic, Optical, and Vibrational Properties of Ultrawide-Band-Gap Semiconductor Materials.
Author:	Mengle, Kelsey.
Published:	Ann Arbor : ProQuest Dissertations & Theses, 2019
Description:	143 p.
Notes:	Source: Dissertations Abstracts International, Volume: 81-11, Section: B.
Notes:	Advisor: Kioupakis, Emmanouil.
Contained By:	Dissertations Abstracts International81-11B.
Subject:	Condensed matter physics.
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=28006571
ISBN:	9798643185819

First-Principles Calculations on the Electronic, Optical, and Vibrational Properties of Ultrawide-Band-Gap Semiconductor Materials.
Mengle, Kelsey.

First-Principles Calculations on the Electronic, Optical, and Vibrational Properties of Ultrawide-Band-Gap Semiconductor Materials. - Ann Arbor : ProQuest Dissertations & Theses, 2019 - 143 p.

Source: Dissertations Abstracts International, Volume: 81-11, Section: B.

Thesis (Ph.D.)--University of Michigan, 2019.

This item must not be sold to any third party vendors.

First-principles calculations enable an unprecedented atomistic insight to experimentally-observed phenomena on a massive scale. Such calculations can intelligently guide experimental efforts to save both human time and money. The methods in this dissertation are first-principles calculations based on density functional theory (DFT), many-body perturbation theory (using the GW method), and density functional perturbation theory (DFPT). With these methods, the electronic, optical, and vibrational properties of beta-Ga2O3, h-BN, and r-GeO2 are calculated and analyzed to assess their promise for deep-ultraviolet luminescence and high-power electronic applications.First, I investigate the near-edge electronic and optical properties of beta-Ga2O3. The fundamental band gap is indirect, but the minimum direct gap is only 29 meV higher in energy, which explains the strong near-edge absorption. Our calculations verify the anisotropy of the absorption onset and explain the range of experimentally reported band-gap values. Our results for the radiative recombination rate indicate that intrinsic light emission in the deep-UV range is possible at high excitation. I calculate the phonon dispersion, which relates to properties such as thermal transport, carrier mobility, and breakdown voltage. The large mode Gruneisen parameters reflect the anharmonicity of monoclinic beta-Ga2O3 and help explain its low thermal conductivity. I also evaluate the electron-phonon coupling matrix elements for the lowest conduction band to determine the phonon mode that limits the mobility at room temperature. I apply these matrix elements to estimate the breakdown field of beta-Ga2O3.A second ultra-wide-band-gap material which shows promise for deep-UV luminescence applications is hexagonal boron nitride (h-BN). I examine the effects of stacking sequence and number of layers on the electronic and luminescence properties of h-BN structures. I explore the variations of the quasiparticle band gap and interband optical matrix elements for bulk, bilayer, and monolayer stacking polytypes. Although the fundamental gap for most structures is indirect, phonon-assisted transitions are strong (typically 600 times stronger than bulk Si) and enable efficient deep-UV luminescence. The polarization of the emitted light is transverse electric, which facilitates light extraction perpendicularly to the h-BN basal plane.Rutile germanium dioxide (r-GeO2) is an ultra-wide-band-gap semiconductor that has not been explored for semiconducting applications in electronic and optoelectronic devices. Our band-structure calculations indicate a dipole-forbidden direct band gap at gamma with an energy of 4.44 eV and relatively low carrier effective masses. The first allowed optical transition at gamma occurs at 5.04 eV (in-plane). I also evaluate the optical absorption coefficient along both crystallographic directions. I theoretically predict the electron and hole mobility of r-GeO2 as a function of temperature. At 300 K, the carrier mobilities (in cm2 V-1 s-1) are muelec = 153.6 (in-plane), muelec = 74.1 (out-of-plane), muhole = 4.7 (in-plane), and muhole = 2.2 (out-of-plane). The thermal conductivities at 300 K are 37 W m-1 K-1 in-plane and 57 W m-1 K-1 out-of-plane. Last, I compare the Baliga’s figure of merit (BFOM) for high-power-electronic applications and show that the BFOM for r-GeO2 surpasses those of competing semiconductors, including beta-Ga2O3.Our theoretical characterization of the electronic, optical, and vibrational properties of beta-Ga2O3, h-BN, and r-GeO2 highlight the viability of these ultra-wide-band-gap semiconductors for applications in deep-UV luminescence and high-power electronics and provides a path for experimental development of materials for improved performance in devices.

ISBN: 9798643185819Subjects--Topical Terms:

708726
Condensed matter physics.
Subjects--Index Terms:

First-principles calculations

First-Principles Calculations on the Electronic, Optical, and Vibrational Properties of Ultrawide-Band-Gap Semiconductor Materials.
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245 1 0 $a First-Principles Calculations on the Electronic, Optical, and Vibrational Properties of Ultrawide-Band-Gap Semiconductor Materials.
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300 $a 143 p.
500 $a Source: Dissertations Abstracts International, Volume: 81-11, Section: B.
500 $a Advisor: Kioupakis, Emmanouil.
502 $a Thesis (Ph.D.)--University of Michigan, 2019.
506 $a This item must not be sold to any third party vendors.
506 $a This item must not be added to any third party search indexes.
520 $a First-principles calculations enable an unprecedented atomistic insight to experimentally-observed phenomena on a massive scale. Such calculations can intelligently guide experimental efforts to save both human time and money. The methods in this dissertation are first-principles calculations based on density functional theory (DFT), many-body perturbation theory (using the GW method), and density functional perturbation theory (DFPT). With these methods, the electronic, optical, and vibrational properties of beta-Ga2O3, h-BN, and r-GeO2 are calculated and analyzed to assess their promise for deep-ultraviolet luminescence and high-power electronic applications.First, I investigate the near-edge electronic and optical properties of beta-Ga2O3. The fundamental band gap is indirect, but the minimum direct gap is only 29 meV higher in energy, which explains the strong near-edge absorption. Our calculations verify the anisotropy of the absorption onset and explain the range of experimentally reported band-gap values. Our results for the radiative recombination rate indicate that intrinsic light emission in the deep-UV range is possible at high excitation. I calculate the phonon dispersion, which relates to properties such as thermal transport, carrier mobility, and breakdown voltage. The large mode Gruneisen parameters reflect the anharmonicity of monoclinic beta-Ga2O3 and help explain its low thermal conductivity. I also evaluate the electron-phonon coupling matrix elements for the lowest conduction band to determine the phonon mode that limits the mobility at room temperature. I apply these matrix elements to estimate the breakdown field of beta-Ga2O3.A second ultra-wide-band-gap material which shows promise for deep-UV luminescence applications is hexagonal boron nitride (h-BN). I examine the effects of stacking sequence and number of layers on the electronic and luminescence properties of h-BN structures. I explore the variations of the quasiparticle band gap and interband optical matrix elements for bulk, bilayer, and monolayer stacking polytypes. Although the fundamental gap for most structures is indirect, phonon-assisted transitions are strong (typically 600 times stronger than bulk Si) and enable efficient deep-UV luminescence. The polarization of the emitted light is transverse electric, which facilitates light extraction perpendicularly to the h-BN basal plane.Rutile germanium dioxide (r-GeO2) is an ultra-wide-band-gap semiconductor that has not been explored for semiconducting applications in electronic and optoelectronic devices. Our band-structure calculations indicate a dipole-forbidden direct band gap at gamma with an energy of 4.44 eV and relatively low carrier effective masses. The first allowed optical transition at gamma occurs at 5.04 eV (in-plane). I also evaluate the optical absorption coefficient along both crystallographic directions. I theoretically predict the electron and hole mobility of r-GeO2 as a function of temperature. At 300 K, the carrier mobilities (in cm2 V-1 s-1) are muelec = 153.6 (in-plane), muelec = 74.1 (out-of-plane), muhole = 4.7 (in-plane), and muhole = 2.2 (out-of-plane). The thermal conductivities at 300 K are 37 W m-1 K-1 in-plane and 57 W m-1 K-1 out-of-plane. Last, I compare the Baliga’s figure of merit (BFOM) for high-power-electronic applications and show that the BFOM for r-GeO2 surpasses those of competing semiconductors, including beta-Ga2O3.Our theoretical characterization of the electronic, optical, and vibrational properties of beta-Ga2O3, h-BN, and r-GeO2 highlight the viability of these ultra-wide-band-gap semiconductors for applications in deep-UV luminescence and high-power electronics and provides a path for experimental development of materials for improved performance in devices.
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653 $a Beta-gallium oxide
653 $a Hexagonal boron nitride
653 $a Rutile germanium dioxide
653 $a High-power electronics
653 $a Deep ultraviolet luminescence
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