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ASU Electronic Theses and Dissertations


This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.

In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.

Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.


Contributor
Date Range
2010 2020


Positron emission tomography (PET) is a non-invasive molecular imaging technique widely used for the quantification of physiological and biochemical processes in preclinical and clinical research. Due to its fundamental role in the health care system, there is a constant need for improvement and optimization of its scanner systems and protocols leading to a dedicated active area of research for PET. (Geant4 Application for Tomographic Emission (GATE) is a simulation platform designed to model and analyze a medical device. Monte Carlo simulations are essential tools to assist in optimizing the data acquisition protocols or in evaluating the correction methods for improved …

Contributors
Thirumalai, Sowmiya Raj, Vasileska, Dragica, Goldan, Amirhossein, et al.
Created Date
2020

This work is concerned with the study and numerical solution of large reaction diffusion systems with applications to the simulation of degradation effects in solar cells. A discussion of the basics of solar cells including the function of solar cells, the degradation of energy efficiency that happens over time, defects that affect solar cell efficiency and specific defects that can be modeled with a reaction diffusion system are included. Also included is a simple model equation of a solar cell. The basics of stoichiometry theory, how it applies to kinetic reaction systems, and some conservation properties are introduced. A model …

Contributors
Shapiro, Bruce G., Ringhofer, Christian, Gardner, Carl L, et al.
Created Date
2020

4H-SiC has been widely used in many applications. All of these benefit from its extremely high critical electric field and good electron mobility. For example, 4H-SiC possesses a critical field ten times higher than that of Si, which allows high-voltage blocking layers composed of 4H-SiC to be approximately a tenth the thickness of a comparable Si device. This, in turn, reduces the device on-resistance and power losses while maintaining the same high blocking capability. Unfortunately, commercial TCAD tools like Sentaurus and Silvaco Atlas are based on the effective mass approximation, while most 4H-SiC devices are not operated under low electric …

Contributors
Cheng, Chi-Yin, Vasileska, Dragica, Goodnick, Stephen M, et al.
Created Date
2020

Wurtzite (In, Ga, Al) N semiconductors, especially InGaN material systems, demonstrate immense promises for the high efficiency thin film photovoltaic (PV) applications for future generation. Their unique and intriguing merits include continuously tunable wide band gap from 0.70 eV to 3.4 eV, strong absorption coefficient on the order of ∼105 cm−1, superior radiation resistance under harsh environment, and high saturation velocities and high mobility. Calculation from the detailed balance model also revealed that in multi-junction (MJ) solar cell device, materials with band gaps higher than 2.4 eV are required to achieve PV efficiencies greater than 50%, which is practically and …

Contributors
Huang, Xuanqi, Zhao, Yuji, Goodnick, Stephen M., et al.
Created Date
2020

This dissertation explores thermal effects and electrical characteristics in metal-oxide-semiconductor field effect transistor (MOSFET) devices and circuits using a multiscale dual-carrier approach. Simulating electron and hole transport with carrier-phonon interactions for thermal transport allows for the study of complementary logic circuits with device level accuracy in electrical characteristics and thermal effects. The electrical model is comprised of an ensemble Monte Carlo solution to the Boltzmann Transport Equation coupled with an iterative solution to two-dimensional (2D) Poisson’s equation. The thermal model solves the energy balance equations accounting for carrier-phonon and phonon-phonon interactions. Modeling of circuit behavior uses parametric iteration to ensure …

Contributors
Daugherty, Robin, Vasileska, Dragica, Aberle, James, et al.
Created Date
2019

Semiconductor devices often face reliability issues due to their operational con- ditions causing performance degradation over time. One of the root causes of such degradation is due to point defect dynamics and time dependent changes in their chemical nature. Previously developed Unified Solver was successful in explaining the copper (Cu) metastability issues in cadmium telluride (CdTe) solar cells. The point defect formalism employed there could not be extended to chlorine or arsenic due to numerical instabilities with the dopant chemical reactions. To overcome these shortcomings, an advanced version of the Unified Solver called PVRD-FASP tool was developed. This dissertation presents …

Contributors
Shaik, Abdul Rawoof, Vasileska, Dragica, Ringhofer, Christian, et al.
Created Date
2019

Silicon photovoltaics is the dominant contribution to the global solar energy production. As increasing conversion efficiency has become one of the most important factors to lower the cost of photovoltaic systems, the idea of making a multijunction solar cell based on a silicon bottom cell has attracted broad interest. Here the potential of using dilute nitride GaNPAs alloys for a lattice-matched 3-terminal 2-junction Si-based tandem solar cell through multiscale modeling is investigated. To calculate the electronic band structure of dilute nitride alloys with relatively low computational cost, the sp^3 d^5 s^* s_N tight-binding model is chosen, as it has been …

Contributors
Zou, Yongjie, Goodnick, Stephen M., Honsberg, Christiana B., et al.
Created Date
2019

Silicon photonic technology continues to dominate the solar industry driven by steady improvement in device and module efficiencies. Currently, the world record conversion efficiency (~26.6%) for single junction silicon solar cell technologies is held by silicon heterojunction (SHJ) solar cells based on hydrogenated amorphous silicon (a-Si:H) and crystalline silicon (c-Si). These solar cells utilize the concept of carrier selective contacts to improve device efficiencies. A carrier selective contact is designed to optimize the collection of majority carriers while blocking the collection of minority carriers. In the case of SHJ cells, a thin intrinsic a-Si:H layer provides crucial passivation between doped …

Contributors
Muralidharan, Pradyumna, Goodnick, Stephen M, Vasileska, Dragica, et al.
Created Date
2019

Gallium Nitride (GaN) based Current Aperture Vertical Electron Transistors (CAVETs) present many appealing qualities for applications in high power, high frequency devices. The wide bandgap, high carrier velocity of GaN make it ideal for withstanding high electric fields and supporting large currents. The vertical topology of the CAVET allows for more efficient die area utilization, breakdown scaling with the height of the device, and burying high electric fields in the bulk where they will not charge interface states that can lead to current collapse at higher frequency. Though GaN CAVETs are promising new devices, they are expensive to develop due …

Contributors
Warren, Andrew, Vasileska, Dragica, Goodnick, Stephen, et al.
Created Date
2019

In this dissertation, I investigate the electronic properties of two important silicon(Si)-based heterojunctions 1) hydrogenated amorphous silicon/crystalline silicon (a-Si:H/c-Si) which has already been commercialized in Heterojunction with Intrinsic Thin-layer (HIT) cells and 2) gallium phosphide/silicon (GaP/Si) which has been suggested to be a good candidate for replacing a-Si:H/c-Si in HIT cells in order to boost the HIT cell’s efficiency. In the first part, the defect states of amorphous silicon (a-Si) and a-Si:H material are studied using density functional theory (DFT). I first employ simulated annealing using molecular dynamics (MD) to create stable configurations of a-Si:H, and then analyze the atomic …

Contributors
Vatan Meidanshahi, Reza, Goodnick, Stephen Marshall, Vasileska, Dragica, et al.
Created Date
2019