Engineering Commons^™

Characterization Of Highly Doped N-Type And P-Type Silicon Carbide Ohmic Contacts, Tanner Rice

Graduate Theses and Dissertations

Silicon Carbide (SiC) is a rather new material that possesses unparalleled properties when compared to Silicon. Due to its larger band gap alongside other thermal properties, SiC can survive in hotter, more radiation intensive environments, whether that be within the crust of the earth or in the reaches of space. As a desirable semiconductor for these applications, CMOS is an especially important device due to its low power consumption. However, creating a good contact between the metal and semiconductor optimally requires two different metals for the n -type and the p-type semiconductor. This greatly increases the processing time, as separate …

Fabrication Of Black Phosphorus Terahertz Photoconductive Antennas, Nathan Tanner Sawyers

Physics Undergraduate Honors Theses

Terahertz (THz) photoconductive antennas (PCAs) using 40nm thin-film flakes of black phosphorus (BP) and hexagonal boron nitride (hBN) have been shown computationally to be capable of THz emission comparable to those based on GaAs [2]. In this paper, I briefly describe the scientific and practical interest in THz emissions and explain what warrants research into black phosphorus as a photoconductive semiconductor in THz devices. Furthermore, I outline the basic principle of how these antennas work and mention alternative designs produced by other researchers in the past. Finally, I summarize the fabrication process of these antennas, as well as the measurements …

Gate-Controlled Quantum Dots In Two-Dimensional Tungsten Diselenide And One-Dimensional Tellurium Nanowires, Shiva Davari Dolatabadi

Graduate Theses and Dissertations

This work focuses on the investigation of gate-defined quantum dots in two-dimensional transition metal dichalcogenide tungsten diselenide (WSe2) as a means to unravel mesoscopic physical phenomena such as valley-contrasting physics in WSe2 flakes and its potential application as qubit, as well as realizing gate-controlled quantum dots based on elementaltellurium nanostructures which may unlock the topological nature of the host material carriers such as Weyl states in tellurium nanowires.The fabrication and characterization of gate-defined hole quantum dots in monolayer and bilayer WSe2 are reported. The gate electrodes in the device design are located above and below the WSe2 nanoflakes to accumulate …

Tailoring Interfaces And Composition For Stable And Efficient Perovskite Solar Cells, Hamza Javaid

Doctoral Dissertations

Metal halide perovskite solar cells (PSCs) have revolutionized the field of thin film photovoltaics. Within a decade, the power conversion efficiencies (PCEs) have increased at a phenomenal rate, rising from 3.8% to more than 25% in single-junction devices, moving them ahead of the current silicon-based technology. The high efficiencies of perovskite solar cells (PSCs) and their other unique properties arise from a combination of organic and inorganic components and electronic-ionic conduction, making them excellent candidates for a plethora of applications. However, PSCs face a significant—and ironic—roadblock to commercialization: these light-harvesting materials degrade under sunlight—the very condition they would need …

Study Of Thick Indium Gallium Nitride Graded Structures For Future Solar Cell Applications, Manal Abdullah Aldawsari

Graduate Theses and Dissertations

Indium gallium nitride (InxGa1-xN) materials have held great potential for the optoelectronic industry due to their electrical and optical properties. The tunable band gap that can span the solar spectrum was one of the most significant features that attracted researchers’ attention. The band gap can be varied continuously from 0.77 eV for InN to 3.42 eV for GaN, covering the solar spectrum from near infrared to near ultraviolet. Additionally, it has a high absorption coefficient on the order of ∼105 cm−1, a direct band gap, high radiation resistance, thermal stability, and so on. Nevertheless, the epitaxial growth of high quality …

Advanced Organic Polymers For The Nanoscale Fabrication Of Fiber-Based Electronics Using The Electrospinning Technique, William Serrano Garcia

USF Tampa Graduate Theses and Dissertations

Electrospinning has become one of the most interesting techniques for fabricating nanofibers for multiple applications. The high surface-to-volume ratio nanofibers offer make the perfect structure for filters, sensors, and fiber-based electronics that could lead to a wide range of flexible electronics applications. This technique makes organic semiconducting polymers a promising alternative for single fiber electronics structures. Indeed, a wide variety of structures can be fabricated using electrostatic techniques for polymer manipulation from droplets, fibers, and coaxial structures. Although techniques such as electrospinning led the use of electrostatic forces to generate fibers of a precursor solution, electrospinning requires large enough polymer …

Design And Characterization Of Standard Cell Library Using Finfets, Phanindra Datta Sadhu

Master's Theses

The processors and digital circuits designed today contain billions of transistors on a small piece of silicon. As devices are becoming smaller, slimmer, faster, and more efficient, the transistors also have to keep up with the demands and needs of the daily user. Unfortunately, the CMOS technology has reached its limit and cannot be used to scale down due to the transistor's breakdown caused by short channel effects. An alternative solution to this is the FinFET transistor technology, where the gate of the transistor is a three dimensional fin that surrounds the transistor and prevents the breakdown caused by scaling …

Characterization Of Gesn Semiconductors For Optoelectronic Devices, Hryhorii Stanchu

Graduate Theses and Dissertations

Germanium-tin alloys with Sn compositions higher than 8 at. % to 10 at. % have recently attracted significant interest as a group IV semiconductor that is ideal for active photonics on a Si substrate. The interest is due to the fact that while at a few percent of Sn, GeSn is an indirect bandgap semiconductor, at about 8 to 10 at. % Sn, GeSn transitions to a direct bandgap semiconductor. This is at first surprising since the solid solubility of Sn in Ge under equilibrium growth conditions is limited to only about 1 at. %. However, under non-equilibrium growth conditions, …

Si-Based Germanium Tin Photodetectors For Infrared Imaging And High-Speed Detection, Huong Tran

Graduate Theses and Dissertations

Infrared (IR) radiation spans the wavelengths of the windows: (1) near-IR region ranging from 0.8 to 1.0 μm, (2) shortwave IR (SWIR) ranging from 1.0 to 3.0 μm, (3) mid-wave IR (MWIR) region covering from 3.0 to 5.0 μm, (4) longwave IR (LWIR) spanning from 8.0 to 12.0 μm, and (5) very longwave IR extending beyond 12.0 μm. The MWIR and LWIR regions are important for night vision in the military, and since the atmosphere does not absorb at these wavelengths, they are also used for free-space communications and astronomy. Automotive and defect detection in the food industry and electronic …

Deposition And Characterization Of Indium Nitride And Aluminum Nitride Thin Films By Reactive Sputtering, Sushma Swaraj Atluri

Electrical & Computer Engineering Theses & Dissertations

Intensive research has been carried out on III-V semiconductors for over a century due to their various applications in the field of Microelectronics, Optics, and Photonics. Among III-V materials, the III-nitrides, for example Aluminum Nitride, Indium Nitride, Gallium Nitride and their ternary alloys are known for their unique properties. All the III-Nitride Compounds are direct bandgap semiconductors with a bandgap ranging from 0.7 eV to 6.2 eV covering the entire visible region and extending to the UV region as well. Despite having many applications, fabricating good quality thin films without defects is quite a challenge. They are typically grown using …

Tailoring The Grain Boundaries Of Wide-Bandgap Perovskite Solar Cells By Molecular Engineering, Khalid Emshadi

Electronic Theses and Dissertations

Due to the attraction of fabricating highly efficient tandem solar cells, wide-bandgap perovskite solar cells have attracted substantial interest in recent years. However, polycrystalline perovskite thin-films show the existence of trap states at grain boundaries, which diminish the optoelectronic properties of the perovskite and thus remains a challenge. This research demonstrates a one-step solution-processing of the [MA_0.9Cs_0.1Pb(I_0.6Br_0.4)3] wide-bandgap perovskite using Phenylhydrazine Iodide with amino groups to successfully passivate the trap density within grain boundaries and increase the perovskite grain size. The reinforced morphology and grain boundaries treatment considerably enhanced the photovoltaic performance …

Epitaxial Growth Of Iii-Nitride Nanostructures And Their Optoelectronic Applications, Moab Rajan Philip

Dissertations

Light-emitting diodes (LEDs) using III-nitride nanowire heterostructures have been intensively studied as promising candidates for future phosphor-free solid-state lighting and full-color displays. Compared to conventional GaN-based planar LEDs, III-nitride nanowire LEDs exhibit numerous advantages including greatly reduced dislocation densities, polarization fields, and quantum-confined Stark effect due to the effective lateral stress relaxation, promising high efficiency full-color LEDs. Beside these advantages, however, several factors have been identified as the limiting factors for further enhancing the nanowire LED quantum efficiency and light output power. Some of the most probable causes have been identified as due to the lack of carrier confinement in …

Investigation Of Electronic And Optical Properties Of 2-Dimensional Semiconductor Tin Selenide (Snse) Thin Films, Shakila Afrin

Dissertations and Theses

Over the last 5 decades, the semiconductor industry has been well served by Si based technology due to its abundant availability, lower manufacturing cost, large wafer sizes and less complexity in fabrication. Over this period, electronic devices and integrated systems have been miniaturized by downscaling of the transistors. The miniaturization has been guided by the Moore's law where the numbers of transistors have doubled over every two years. However, the trend of transistor miniaturization is fast approaching its limit. Hence, alternate and innovative solutions are necessary to tackle this problem and this propels the research for finding novel materials with …

Exploring Gated Nanoelectronic Devices Fabricated From 1d And 2d Materials, Prathamesh A. Dhakras

Legacy Theses & Dissertations (2009 - 2024)

One and two dimensional materials are being extensively researched toward potential application as ultra-thin body channel materials. The difficulty of implementing physical doping methods in these materials has necessitated various alternative doping schemes, the most promising of which is the electrostatic gating technique due to its reconfigurability. This dissertation explores the different fundamental devices that can be fabricated and characterized by taking advantage of the electrostatic gating of individual single-walled carbon nanotubes (SWNTs), dense SWNT networks and exfoliated 2D tungsten diselenide (WSe2) flakes.

Generalizable Modeling Of Charge Transport In Single Electron Transistor Devices: Application To Thermal Sensitivity In Semiconducting Island Systems, Paniz Khanmohammadi Hazaveh

Dissertations, Master's Theses and Master's Reports

Electronic devices, especially MOSFETs, have been dimensionally scaled down to enhance operation of integrated circuits, addressing challenges such as current leakage, fluctuation of intrinsic semiconductor properties, and power dissipation. Reaching dimensions below 20 nm, there are fundamental limitations that are difficult to overcome, driving alternative device paradigms to be sought utilizing the quantum mechanical behavior of electrons. Single electron transistor (SET) devices are examples of a new generation of low-power transistors designed to transport information via single electron tunneling through one or more islands separated by tunnel junctions. Experimentally explored SET devices have shown that there are advantages to using …

Progress Towards Competitive Iii-V Infrared Detectors: Fundamental Material Characterization And Techniques, Emil A. Kadlec

Electrical and Computer Engineering ETDs

Measurement of recombination mechanisms provides critical feedback on the material quality of semiconductors. Strained layer type-II superlattices (T2SLs) have seen a recent increase in interest as they possess intriguing properties making them prime candidates for use as infrared detectors. As T2SL-based detectors approach the performance of industry-standard Hg_1-xCd_xTe photodetectors, measurement of the carrier lifetime is becoming increasingly important. A comparison of the lifetime measurement techniques time-resolved photoluminescence, frequency-modulated photoluminescence, time-resolved microwave reflectance, and frequency-modulated conductance is made. Although photoluminescence-based measurement techniques are more common in literature, it is shown that the microwave reflectance-based measurement technique is …

Structural And Electrical Characterization Of Single Crystalline Srzrxti₁-Xo₃ Thin Films On Germanium, Reza Matthew Moghadam

Electrical Engineering Dissertations

The epitaxial growth of crystalline oxides on semiconductors provides a pathway to introduce new functionalities to semiconductor devices. Key to coupling crystalline oxides to semiconductors electrically, to realize functional behavior, is controlling the manner in which their bands align at the interfaces. This document reports on the three research projects on Crystalline Oxide/Semiconductor heterostructures. In the first project we applied principles of band-gap engineering traditionally used at heterojunctions between conventional semiconductors to control the band offset between a single crystalline oxide and a semiconductor. Reactive molecular beam epitaxy is used to realize atomically abrupt and structurally coherent interfaces between SrZrxTi1-xO3 …

The Impact Of Quantum Size Effects On Thermoelectric Performance In Semiconductor Nanostructures, Adithya Kommini

Masters Theses

An increasing need for effective thermal sensors, together with dwindling energy resources, have created renewed interests in thermoelectric (TE), or solid-state, energy conversion and refrigeration using semiconductor-based nanostructures. Effective control of electron and phonon transport due to confinement, interface, and quantum effects has made nanostructures a good way to achieve more efficient thermoelectric energy conversion. This thesis studies the two well-known approaches: confinement and energy filtering, and implements improvements to achieve higher thermoelectric performance. The effect of confinement is evaluated using a 2D material with a gate and utilizing the features in the density of states. In addition to that, …

Control Of Cation Ordering In Zinc Tin Nitride And In-Situ Monitoring Of Growth, Brian Christopher Durant

Masters Theses

Semiconducting materials with a band gap around 1.5 eV are very much sought after due to their close match to the solar spectrum. However, some compounds that have shown promise for highly efficient solar cells contain rare, expensive, and sometimes toxic elements, such as indium and gallium. As such, a search for earth abundant materials has become more prominent recently. One such earth abundant semiconducting material that has garnered interest is ZnSnN₂. It has been shown through previous studies that there is the possibility of continuously tuning the band gap between 1.0 and 2.0 eV by controlling the …

Molecular Dynamics Study On Defect Reduction Strategies Towards The Fabrication Of High Performance Cd1-Xznxte/Cds Solar Cells, Jose Juan Chavez

Open Access Theses & Dissertations

Cadmium Telluride is a material widely used in terrestrial thin film photovoltaic applications due to its nearly ideal band gap (~1.5 eV) and high absorption coefficient. Due to its low manufacturing cost, this technology has the potential to become a significant energy resource if higher energy conversion efficiencies are achieved. However, the module efficiencies (~14%) are still far from the theoretical maximum (~30%) for this material in a single junction configuration. The reason behind this low performance is attributed to the high number of defects that are present within the device materials. The physics behind the formation mechanisms of these …

Two-Photon Absorption In Bulk Semiconductors And Quantum Well Structures And Its Applications, Himansu Pattanaik

Electronic Theses and Dissertations

The purpose of this dissertation is to provide a study and possible applications of two-photon absorption (2PA), in direct-gap semiconductors and quantum-well (QW) semiconductor structures. One application uses extremely nondegenerate (END) 2PA, for mid-infrared (mid-IR) detection in uncooled semiconductors. The use of END, where the two photons have very different energies gives strong enhancement comapared to degenerate 2PA. This END-2PA enhanced detection is also applied to mid-IR imaging and light detection and ranging (LIDAR) in uncooled direct-gap photodiodes. A theoretical study of degenerate 2PA (D-2PA) in quantum wells, QWs, is presented, along with a new theory of ND 2PA in …

Gallium Nitride: Analysis Of Physical Properties And Performance In High-Frequency Power Electronic Circuits, Dalvir K. Saini

Browse all Theses and Dissertations

Gallium nitride (GaN) technology is being adopted in a variety of power electronic applications due to their high efficiencies even at high switching speeds. In comparison with the silicon (Si) transistors, the GaN-based devices exhibit lower on-state resistance and parasitic capacitances. The thermal performance of the GaN transistors are also better than the Si counterparts due to their higher junction temperature and lower temperature-coefficient of on-resistance. These unique properties make the gallium-nitride power transistors an appropriate selection for power electronic converters and radio-frequency power amplifiers, where size, efficiency, power density, and dynamic performance are major requirements.

Foreseeing the immense capabilities …

Oxide Defect Engineering Methods For Valence Change (Vcm) Resistive Random Access Memories, Jihan Ocampo Capulong

Legacy Theses & Dissertations (2009 - 2024)

Electrical switching requirements for resistive random access memory (ReRAM) devices are multifaceted, based on device application. Thus, it is important to obtain an understanding of these switching properties and how they relate to the oxygen vacancy concentration and oxygen vacancy defects. Oxygen vacancy defects in the switching oxide of valence-change-based ReRAM (VCM ReRAM) play a significant role in device switching properties. Oxygen vacancies facilitate resistive switching as they form the conductive filament that changes the resistance state of the device. This dissertation will present two methods of modulating the defect concentration in VCM ReRAM composed of Pt/HfO_x/Ti stack: …

Ultrafast Laser Material Processing For Photonic Applications, Mark Ramme

Electronic Theses and Dissertations

Femtosecond Laser Direct Writing (FLDW) is a viable technique for producing photonic devices in bulk materials. This novel manufacturing technique is versatile due to its full 3D fabrication capability. Typically, the only requirement for this process is that the base material must be transparent to the laser wavelength. The modification process itself is based on non-linear energy absorption of laser light within the focal volume of the incident beam. This thesis addresses the feasibility of this technique for introducing photonic structures into novel dielectric materials. Additionally, this work provides a deeper understanding of the lightmatter interaction mechanism occurring at high …

Crystal Growth, Characterization And Fabrication Of Cdznte-Based Nuclear Detectors, Ramesh Madhu Krishna

Theses and Dissertations

In today's world, nuclear radiation is seeing more and more use by humanity as time goes on. Nuclear power plants are being built to supply humanity's energy needs, nuclear medical imaging is becoming more popular for diagnosing cancer and other diseases, and control of weapons-grade nuclear materials is becoming more and more important for national security. All of these needs require high-performance nuclear radiation detectors which can accurately measure the type and amount of radiation being used. However, most current radiation detection materials available commercially require extensive cooling, or simply do not function adequately for high-energy gamma-ray emitting nuclear materials …

Characterization And Modeling Of 4h-Sic Low Voltage Mosfets And Power Mosfets, Mihir Mudholkar

Graduate Theses and Dissertations

The integration of low voltage and high voltage circuits on SiC has profound applications. SiC power devices have proved their superiority in terms of high temperature operation, faster switching frequencies and larger power densities when compared with Si power devices. The control of SiC power devices however, lies in the hands of low voltage circuits built on Si. Thus, there exists a separation in the overall system between the low voltage and high voltage side, which increases system cost, weight and reduces efficiency. With the advancement in low voltage SiC processing technology, low voltage control circuits can be made on …

Experimental And Theoretical Approaches To Characterization Of Electronic Nonlinearities In Direct-Gap Semiconductors, Claudiu Cirloganu

Electronic Theses and Dissertations

The general goal of this dissertation is to provide a comprehensive description of the limitations of established theories on bound electronic nonlinearities in direct-gap semiconductors by performing various experiments on wide and narrow bandgap semiconductors along with developing theoretical models. Nondegenerate two-photon absorption (2PA) is studied in several semiconductors showing orders of magnitude enhancement over the degenerate counterpart. In addition, three-photon absorption (3PA) is studied in ZnSe and other semiconductors and a new theory using a Kane 4-band model is developed which fits new data well. Finally, the narrow gap semiconductor InSb is studied with regard to multiphoton absorption, free-carrier …

Nonlinear Absorption And Free Carrier Recombination In Direct Gap Semiconductors, Peter D. Olszak

Electronic Theses and Dissertations

Nonlinear absorption of Indium Antimonide (InSb) has been studied for many years, yet due to the complexity of absorption mechanisms and experimental difficulties in the infrared, this is still a subject of research. Although measurements have been made in the past, a consistent model that worked for both picosecond and nanosecond pulse widths had not been demonstrated. In this project, temperature dependent two-photon (2PA) and free carrier absorption (FCA) spectra of InSb are measured using femtosecond, picosecond, and nanosecond IR sources. The 2PA spectrum is measured at room temperature with femtosecond pulses, and the temperature dependence of 2PA and FCA …

Effect Of Mechanical Vibrations On Light Emitting Diode Luminaires, Jayalakshmi Paladugu

UNLV Theses, Dissertations, Professional Papers, and Capstones

In this work, a LED and two types of Compact fluorescent lamps were investigated for the intensity variation due to mechanical vibrations in the range of 0 to 30 HZ. In general, subjecting the lamps to 24-hour vibration affects the total intensity percentage variations of peak intensities after vibrations is in the range of -25 to +15% compared to those of no vibrations for the light emitting diode luminaires. For the case of compact fluorescent lamps (Nuvue) the variations are in range from +10 to +35%, whereas for the Compact fluorescent lamps (Ecosmart) the intensity peaks range from -10 to …

Individual Copper Nanowire Decorated By Gold Nanoparticles For Surface Enhanced Raman Scattering, Roshan Guttikonda

UNLV Theses, Dissertations, Professional Papers, and Capstones

In this Thesis, I discuss the theory, implementation and applications of Surface enhanced Raman scattering (SERS). Surface enhanced Raman scattering has been used to detect 4 mercaptopyridine molecules. On a Silicon wafer, Gold nanoparticles are deposited onto Copper nanowires. Hotspots occur at the small gap (less than 10nm) between the nanowire and nanoparticle. The interaction of the electromagnetic field of the incident laser and the surface plasmon resonances of the metal nanoparticles at the hot spots enhances the Raman scattering signal of the adsorbed pyridine molecule (10 -3 M ). The dependence of SERS signal on the polarization angle of …