Design, Fabrication And Characterization Of Zero Power Sensor/Harvester For Smart Grid Applications, Zeynel Guler

Mechanical Engineering ETDs

This study presents a flexible sensor/harvester device to be used in both electromagnetic sensing and energy harvesting applications for smart grids. When a current passes through a wire, the sensor detects the magnetic field created by that current. The sensor magnet interacts with the wire magnetic field resulting in a transfer of energy through the piezoelectric cantilever. Piezoelectric, conductive, magnetic, and magnetostrictive composite thin films were prepared to fabricate this device.

Initially, the magnet of the cantilever was optimized considering its shape, thickness, length, taper angle etc. via both simulations and experiments. Peak to peak voltage versus cantilever position graph …

Carrier Dynamics In Green Iii-Nitride Leds Using Small-Signal Electroluminescence, Xuefeng Li

Optical Science and Engineering ETDs

Solid-state lighting has achieved significant success over the past two decades, but the low quantum efficiency of green LEDs (i.e., the “green gap”) remains a barrier to full red-green-blue (RGB) displays in numerous applications. Combating efficiency reduction in longer-wavelength LEDs requires understanding the relative roles of intrinsic effects (e.g., wave-function overlap, carrier-current density relationship, phase-space filling (PSF)) vs. extrinsic effects (e.g., material degradation due to increased defect density, compositional inhomogeneities, etc.). A systematic study of the carrier dynamics in InGaN/GaN LEDs is very important for understanding the origin of the green gap and for providing solutions to improve the efficiency …

Machine Learning Based Prediction Models For Silicon Heterojunction Solar Cell Optimization, Rahul Jaiswal

Electrical and Computer Engineering ETDs

Silicon heterojunction solar cell of Heterojunction with Thin Intrinsic Layer (HIT) structure is a commercially available technology, and its market share will significantly increase by the next decade. With such a significant market share, any minor improvement in the device’s overall efficiency can be beneficial three folds - customer return on investment, industry revenue, and the overall carbon footprint (from manufacturing to recycling/ disposing of the device). Conventionally, device optimization for solar cells has been achieved using a hit & trial approach where multiple experiments are done to evaluate the best process conditions and device parameters. This approach has some …

Material Characterization And Comparison Of Sol-Gel Deposited And Rf Magnetron Deposited Lead Zirconate Titanate Thin Films, Katherine Lynne Miles

Mechanical Engineering ETDs

Lead zirconate titanate (PZT) has been a material of interest for sensor, actuator, and transducer applications in microelectromechanical systems (MEMS). This is due to their favorable piezoelectric, pyroelectric and ferroelectric properties. While various methods are available to deposit PZT thin films, radio frequency (RF) magnetron sputtering was selected to provide high quality PZT films with the added capability of batch processing. These sputter deposited PZT films were characterized to determine their internal film stress, Young’s modulus, composition, and structure. After characterization, the sputtered PZT samples were poled using corona poling and direct poling methods. As a means of comparison, commercially …

Gamma And Neutron Irradiation Effect On Ga-Polar And N-Polar Gan Based Diodes, Farnood Mirkhosravi

Optical Science and Engineering ETDs

III-nitride material (GaN) shows a lot of potential for next-generation power electronics. This material is advantageous due to its wide bandgap, high electron mobility, high thermal and mechanical stability, small form factor, and higher radiation tolerance. The higher radiation tolerance makes the GaN-based devices more attractive for harsh-environment applications, like aerospace, nuclear reactor, and fusion facilities, particle accelerators, and post-detonation environments applications.

GaN due to its unique crystal structure can be grown in different orientations and can provide specific advantages in electronic and optoelectronic devices. While the Ga-polar orientation of GaN has been widely investigated for its proprieties, there are …

Device-Level Predictive Modeling Of Extreme Electromagnetic Interference, Nishchay H. Sule

Electrical and Computer Engineering ETDs

Radio Frequency (RF) interference is a prominent issue for modern electronic devices. As device size and supply power shrink to meet the on-going demand for compact and complex Integrated Circuits (ICs), their susceptibility to external noise coupling to the input or power supply increases significantly. One such type of noise that acts upon a system to be considered is Extreme Electromagnetic Interference (EEMI). Previous works done to understand and evaluate the impact of EEMI onto a system or sub-system have been conducted on a statistical or empirical analysis level, which has led to complex and convoluted analysis, that requires significant …

Optical Angular Scatterometry: In-Line Approach For Roll-2-Roll And Nano-Imprint Fabrication Systems, Juan Jose Faria-Briceno

Electrical and Computer Engineering ETDs

As critical dimensions continue to shrink and structures become more complex, metrology processes are challenging to implement during in-line nanomanufacturing. Non-destructive, non-contact, and high-speed conditions are required to achieve proper metrology processes during in-line manufacturing. Optical scatterometry is a nanoscale metrology tool widely used in integrated circuit manufacturing for characterization and quality control. However, most applications of optical scatterometry operate off-line. A high-speed, in-line, non-contact, non-destructive scatterometry angular system has been demonstrated in this work to scan pattern surfaces during real-time nano-fabrication.

Our system has demonstrated scanning capabilities using flat, 1D and 2D complex structures. The flat surface samples consist …

Integrated Chirped-Grating Spectrometer-On-A-Chip, Shima Nezhadbadeh

Optical Science and Engineering ETDs

In this dissertation we demonstrate a new structure based on waveguide coupling atop a silicon wafer using a chirped grating to provide the dispersion that leads to a high-resolution, compact, fully integrable and CMOS-compatible spectrometer. Light is both analyzed and detected in a single, completely monolithic component which enables realizing a high-resolution portable spectrometer with an extremely compact footprint. The structure is comprised of a SiO₂/Si₃N₄/SiO₂ waveguide on top of a silicon wafer. Grating regions are fabricated on the top cladding of the waveguide. The input light is incident on a chirped grating …

Pixelated Gasb Membranes For Photovoltaics: Fabrication And Structure-Property Relationships, Vijay Saradhi Mangu

Electrical and Computer Engineering ETDs

In this thesis, I present a reliable and efficient approach to heterogeneous integration of single-crystalline GaSb semiconductors with highly mismatched materials. The mismatch may refer to the crystalline structure and the thermal expansion coefficient of single-crystalline GaSb and the other materials of interest. The strategy of hetero-integration relies on epitaxial lift-off. This approach prevents the formation of extended structural defects that are detrimental to the performance of optoelectronic devices and preserves GaSb growth substrates for potential reuse.

Within my research work, I have overcome some outstanding challenges of epitaxial lift-off of GaSb, and I have demonstrated the operation of single-crystalline …

Symmetry And Dopant Diffusion In Inverted Nanopyramid Arrays For Thin Crystalline Silicon Solar Cells, Seok Jun Han

Chemical and Biological Engineering ETDs

In this dissertation, we enhance the efficiency of thin flexible monocrystalline silicon solar cells by breaking symmetry in light trapping nanostructures and improving homogeneity in dopant concentration profile. These thin cells are potentially less expensive than conventional thick silicon cells by using less silicon material and making the cells more convenient to be handled when supported on polymer films. Moreover, these cells are widely applicable due to their flexibility and lightweight. However, for high efficiencies, these cells require effective light trapping and charge collection. We achieve these in cells based on 14-mm-thick free-standing silicon films with light-trapping arrays of nanopyramidal …

Algorithmic Multi-Color Cmos Avalanche Photodiodes For Smart-Lighting Applications, Md Mottaleb Hossain

Optical Science and Engineering ETDs

Future smart-lighting systems are expected to deliver adaptively color-tunable and high-quality lighting that is energy efficient while also offering integrated visible-light wireless communication services. To enable these systems at a commercial level, inexpensive and fast sensors with spectral-sensing capability are required. CMOS-compatible silicon avalanche photodiodes (APDs) can be an excellent fit to this problem due to their excellent sensitivity, high speeds and cost effectiveness; however, color sensing is a challenge without resorting to expensive spectral filters, as done in commercially. To address this challenge, we have recently designed and modeled a novel CMOS-compatible dual-junction APD. The device outputs two photocurrents …

Vertical Transport Study Of Iii-V Type-Ii Superlattices, Zahra Taghipour

Optical Science and Engineering ETDs

Type-II strained layer superlattice (T2SL) semiconductors hold great promise for mid- and long-wavelength infrared photodetectors. While T2SL-based materials have advanced significantly in the last three decades, an outstanding challenge to improve the T2SLs is to understand the carrier transport and its limitations, in particular along the superlattice growth layers.

In this dissertation, an overview of the current state-of-the-art InAs/GaSb T2SLs is presented. Fundamental semiconductor device equations and transport properties, including miniband conduction and the drift-diffusion parameters, are reviewed, and the fundamental limiting factors in carrier's transport are discussed. Furthermore, the standard method of electron-beam-induced current technique to measuring these parameters …

Genetic Algorithm Design Of Photonic Crystals For Energy-Efficient Ultrafast Laser Transmitters, Troy A. Hutchins-Delgado

Shared Knowledge Conference

Photonic crystals allow light to be controlled and manipulated such that novel photonic devices can be created. We are interested in using photonic crystals to increase the energy efficiency of our semiconductor whistle-geometry ring lasers. A photonic crystal will enable us to reduce the ring size, while maintaining confinement, thereby reducing its operating power. Photonic crystals can also exhibit slow light that will increase the interaction with the material. This will increase the gain, and therefore, lower the threshold for lasing to occur. Designing a photonic crystal for a particular application can be a challenge due to its number of …

Tunneling In Si Mos Nanostructures, Amir Shirkhorshidian

Electrical and Computer Engineering ETDs

In this dissertation, split-gate tunnel barriers in enhancement-mode silicon metal- oxide-semiconductor (MOS) device structures are characterized electrically at liquid helium temperatures (T = 4.2 K) using transport spectroscopy. Tunnel barriers with different gate geometries and barriers implanted with a small number of antimony donor atoms are characterized. Low disorder MOS tunnel barriers are demonstrated and compared to the implanted cases. The ”clean” MOS tunnel barriers are an important proof of principle that disorder free tunnel barriers can be achieved in MOS. The implanted cases provide an important reference for the effects of donors and shallow traps on a MOS tunnel …

Selected Applications Of Silicon Nanopillar Arrays., Behnam Kheyraddini Mousavi

Electrical and Computer Engineering ETDs

Interaction of optical waves with nanostructures made of various material systems has been the subject of intensive research for many years. These researches have been mainly driven by the need to make smaller optical devices and exploiting the functionalities offered by light-matter interaction in nanoscale. Majority of the nanostructures are fabricated using electron beam (e-beam) lithography that is slow and expensive. As such alternative methods have been developed to enable nanoscale fabrication faster and less expensive. Among these interferometric lithography (IL) is a relatively simple method for quick fabrication of nanostructures. As IL method generates periodic patterns, exploring the potential …

Integration Of Thin Film Tpv Cells To Cvd Diamond Heat Spreaders, Emma J. Renteria

Electrical and Computer Engineering ETDs

In this work, techniques to isolate thermophotovoltaic (TPV) devices from the growth substrate and their subsequent integration with Chemical Vapor Deposition (CVD) diamond heat spreaders will be discussed, with the envisioned goal of fabricating thermally managed cells. CVD diamond heat spreaders are a great option for thermal management of TPV cells. The key requirement, however, is the bonding of the TPV cell directly onto the diamond wafer without the presence of thick (>350 μm) growth substrates, which can offer significant thermal resistance.

The first approach is to release GaSb epitaxial layers from GaSb substrates. However, this is challenging due …

Design & Evaluation Of A Hybrid Switched Capacitor Circuit With Wide-Bandgap Devices For Dc Grid Applications, Joshua L. Stewart

Electrical and Computer Engineering ETDs

ABSTRACT

As technologies advance, the rate at which renewable power sources, such as solar photovoltaic (PV) and wind, are being added to the power grid is increasing. Typically, PV power plants require large inverters for direct current to alternating current (DC-AC) power conversion, as well as large transformers to step up voltages to the grid voltage. Offshore wind farms and large PV power plants in remote locations often aggregate power on a DC bus in order to improve efficiency and reduce the cost of power conversion hardware within the energy complex. However, the power must still be converted to AC …

The Effect Of Power Supply Ramp Time On Sram Puf's, Abdelrahman T. Elshafiey Mr.

Electrical and Computer Engineering ETDs

Physical unclonable functions (PUFs) are security primitives that exploit the device mismatches. PUFs are a promising solution for hardware cryptography and key storage. They are used in many security applications including identification, authentication and key generation. SRAM is one of the popular implementations of PUFs. SRAM PUFs offer the advantage, over other PUF constructions, of reusing resources (memories) that already exist in many designs.

In this thesis, for the first time, it is demonstrated that the start-up value of an SRAM PUF could be different depending on the SRAM power supply rising time. An analytical model has been developed to …

Measurement And Analysis Of Iii-V & Ii-Vi Infrared Detectors: Radiometric, Noise Spectrum, And Radiation Tolerance Performance, Vincent M. Cowan

Nanoscience and Microsystems ETDs

Infrared (IR) hybrid detector arrays and discrete detectors operated in the space environment may be subjected to a variety of sources of natural radiation while in orbit. This means IR detectors intended for applications such as space-based intelligence, surveillance, and reconnaissance (ISR) or space-situational awareness (SSA) must not only have high performance (high quantum efficiency, h and low dark-current density, J_D, and preferably minimal 1/f noise content), but also their radiation tolerance or ability to withstand the effects of the radiation they would expect to encounter in space must be characterized and well understood. As the effects of …

High Power Optically Pumped Semiconductor Lasers For Sodium Guidestar Applications, Shawn W. Hackett

Optical Science and Engineering ETDs

Optically pumped semiconductor lasers (OPSLs) are shown to provide a much more compact and less expensive source for illumination of the sodium layer of the mesosphere for use as a sodium laser guidestar via single and two photon excitation schemes. This represents a revolution in laser guidestar technology as the cost, size, and power requirements for a laser guidestar system are shown to have been decreased by an order of magnitude with guidestar performance shown to be similar to previous sources. Sodium laser guidestar sources for broadband simultaneous illumination of multiple lines are developed and simulated. Simulations are then compared …

Surface Micromachined Pressure Sensors, William P. Eaton Iv

Electrical and Computer Engineering ETDs

Surface micromachined pressure sensors were designed, modeled, fabricated, and tested. They employed a piezoresistive transduction mechanism and were based upon circular diaphragms, which vary from 50 to 1000 μm in diameter and 1 to 2 μm in thickness. The piezoresistors were placed in Wheatstone bridge configurations to provide simple signal amplification and first order temperature compensation.

Of the different micromachining techniques, surface-micromachining has the advantage of being the most similar to integrated circuit manufacturing. Hence an existing IC equipment set can be used to create mechanical structures. Furthermore, the monolithic integration of a mechanical device with control electronics is simpler …