Engineering Commons^™

Development Of Micro-Sized Algan Deep Ultraviolet Light Emitting Diodes And Monolithic Photonic Integrated Circuits, Richard Speight Floyd Iii

Theses and Dissertations

III-Nitride materials-based visible emission LEDs have emerged as a disruptive technology in the fields of lighting,ⁱ) communications,^ii,iii,iv) and displays.^v,vi) Shorter wavelength LEDs in the DUV spectral region (210nm – 360nm) with ultra-wide bandgap (UWBG) Al_xGa_1-xN active layers are now poised to displace toxic Mercury-based light sources.^vii) Over the past decade AlGaN LEDs operating in the deep ultra-violet (DUV) spectral region (200 nm < λ_emission < 300 nm) have been deployed in novel applications including autonomous drone-based sterilization and sanitization systems, ^viii) point-of-use water purification systems, ^ix) photo-therapeutics,x) gas sensors,xi) and non-line-of-sight (NLOS) communications.^xii) Similarly, DUV light detectors using ultra-wide bandgap (UWBG) Al …

Iii-Nitride Nanostructures: Photonics And Memory Device Applications, Barsha Jain

Dissertations

III-nitride materials are extensively studied for various applications. Particularly, III-nitride-based light-emitting diodes (LEDs) have become the major component of the current solid-state lighting (SSL) technology. Current III-nitride-based phosphor-free white color LEDs (White LEDs) require an electron blocking layer (EBL) between the device active region and p-GaN to control the electron overflow from the active region, which has been identified as one of the primary reasons to adversely affect the hole injection process. In this dissertation, the effect of electronically coupled quantum well (QW) is investigated to reduce electron overflow in the InGaN/GaN dot-in-a-wire phosphor-free white LEDs and to improve the …

Characterization Of High Temperature Optocoupler For Power Electronic Systems, David Gonzalez

Electrical Engineering Undergraduate Honors Theses

High-temperature devices have been rapidly increas due to the implementation of new technologies like silicon carbide, high-temperature ceramic, and others. Functionality under elevated temperatures can reduce signal integrity reducing the reliability of power electronic systems. This study presents an ongoing research effort to develop a high-temperature package for optocouplers to operate at higher temperature compared with commercial devices. Low temperature co-fired ceramic (LTCC) was used as the substrate. Bare die commercial LED and photodetectors were attached to the substrate and tested for functionality. Preliminary results show enhanced performance at elevated temperatures compared to a commercial optocoupler device.

Ac Direct Drive Led Lighting Using Low Cost Analog Components, Miles Head

Master's Theses

This project explores the rapidly expanding area of AC direct drive for LED lighting. AC LED driving does not use typical DC-DC converter-based driving but uses semiconductor switches and a linear regulator to activate a number of LEDs proportional to the input voltage at any given time. This allows bulky, expensive magnetics to be eliminated from the system. The goal of this project was to design a scaled-down physical AC LED direct drive system to validate the conclusions of methods for improving efficiency from a previous investigation that found minimizing voltage across the linear regulating MOSFET led to higher efficiency …

Displacement Damage Effects In Gesn Light Emitting Diodes, Kevin K. Choe

Theses and Dissertations

Potential future use on Earth-orbiting satellites calls for investigation into the suitability of GeSn based photonic devices in high energy proton environments. The electroluminescence (EL) intensity of Ge1-xSnx (x = 0, 0.02, 0.069, and 0.094) light emitting diodes was measured before and after irradiation by 2 MeV protons at relatively high fluence levels. The results showed that GeSn devices with higher Sn content were up to 10 times more resistant against proton displacement damage than the pure Ge (x = 0) devices. As Sn concentration increased, the band gap decreased, and V-P hole trap energy level moved further from the …

Investigating Efficiency Of Ac Direct Drive Of Led Lighting, Miles Davis Head

Electrical Engineering

This project explores the rapidly-expanding area of AC direct drive for LED lighting. AC LED driving does not use typical DC-DC converter-based driving but uses semiconductor switches and a linear regulator to activate a number of LEDs proportional to the input voltage at any given time. This allows bulky, expensive magnetics to be eliminated from the system. The goal of this project was to develop a flexible simulation of a common AC LED system to find areas of significant power loss and attempt to improve them. This allows future versions of an AC LED system to start with major loss …

Smart And Sustainable Aquaponics, Ryan Toal, Kevin Claggett, Justin Goh

Electrical and Computer Engineering Senior Theses

As the global population increases, new ways of sustainable and efficient food production need to be explored in order to meet the growing demand from society. In this paper we explore the methods and functionality of an off-grid, semi-autonomous aquaponics system. This system will serve as a proof of concept for a large scale aquaponics system which can be modelled in other parts of the world where arable land is scarce. It was found that though the initial startup costs are high, it will be able to reduce the cost of food in the long run. The system implements a …

Adaptive Light Dimmer, Jonathan Sato, William Xiong

Electrical Engineering

This project, the Adaptive Light Dimmer for the DC House, senses a room's light content and adjusts a lamp's light intensity accordingly, thus regulating the room's light content. The device is designed to work with renewable energy sources such as wind and solar energy. This would be useful in less developed countries where AC electricity is not well spread and renewable DC, such as solar, can be better utilized. It functions by using the TSL2561 light sensor to sense light, ATTiny85 microcontroller to output PWM to the LED driver, LT3795 LED driver to output current to an LED and LT3014 …

An Electrolytic Capacitor-Less Approach To Eliminating Flicker In Led Lighting, Alex M. Kavouras Sr.

Browse all Theses and Dissertations

In today's lighting industry, there is a high demand for quality, long-lasting light bulbs. Light emitting diodes offer the means for long-life bulbs, while producing a quality output. The issue with the current state of solid-state lighting is how to drive LEDs and maintain their full potential. Many solutions offer either a long-life bulb or a high quality output. The trade-off for a long-lasting bulb typically comes with an output quality that is visibly or invisibly flickering. In order to effectively eliminate flicker from the output of the LED, a large output capacitor is needed. An electrolytic capacitor is a …

Power Supply For Driving High Power Leds With Wireless Control, Joshua C. Avery

Computer Engineering

This project is the design of a power supply for driving high power light emitting diodes (LEDs) with wireless control. The project is divided into two sections, the power supply for driving the LED lights, and the wireless control and fan power supply.

Wireless Led Motorcycle Jacket, Sean O'Brien

Electrical Engineering

In 2013 there were over 120,000 motorcycle fatalities in the U.S. alone, 73% of which were in the evening or during poor lighting conditions. Motorcyclists are at a disadvantage when it comes to their visibility on the road due to their size and location of lighting indicators. Because of this, motorcyclists are 82% more likely to be in an accident than other automobiles. One of the most common phrases among drivers involved in car vs motorcycle collisions is “I just didn’t see him."

Many products exist on the market to assist with visibility of motorcyclists including high-visibility clothing and gear …

Adaptive Automotive Lighting Systems, Marc W. Haeberlin

Master's Theses

Over the past few years, the use of LEDs within the automotive and avionic industries has increased due to their high efficiency, durability and wide range of light brightness. As the use of LEDs within these industries grows, a need for reliable, high performance drivers becomes more relevant. Companies are implementing LEDs for applications involving adaptive lighting or simple dimming features. This thesis shows implementation of various non-isolated analog converters integrated with digital dimmers to achieve these adaptive lighting systems. Adaptive lighting systems involve reading an input from an external source (brake pedal or steering wheel) and changing the brightness …

Led Learning Guitar, Kellen C. Reusser, Justin Fiser

Williams Honors College, Honors Research Projects

The goal of this project is to create an electric guitar that detects and displays chords in different tunings for learning and exploration purposes. A hexaphonic pickup will generate the required signals and a processor will detect the pitch. The computer software will apply the pitch information to determine the tuning and the voicings of chords. LEDs mounted on the fretboard of the guitar will indicate a note to be played.

Electronic Learning Guitar, Justin Fiser

Williams Honors College, Honors Research Projects

No abstract provided.

Piezoelectric Powered Led Street Reflector, Collin Shane Douglass

Electrical Engineering

In many areas of Washington, it rains for a majority of the year. During rainy weather it becomes difficult to see street lanes and dividers, causing hazardous road conditions. The Piezoelectric Powered LED Street Reflector solves this problem. The PPL Street Reflector modifies a street reflector with LED lights. These lights help drivers clearly see where dividers and street lines are in non-ideal weather conditions, such as rain, fog, and snow. The PPL Street Reflector capabilities include harvesting energy through the Piezoelectric Effect, creating a self-sustaining device with minimal maintenance.

Optical Characterization Of Ingan Heterostructures For Blue Light Emitters And Vertical Cavity Lasers: Efficiency And Recombination Dynamics, Serdal Okur

Theses and Dissertations

OPTICAL CHARACTERIZATION OF INGAN HETEROSTRUCTURES FOR BLUE LIGHT EMITTERS AND VERTICAL CAVITY LASERS: EFFICIENCY AND RECOMBINATION DYNAMICS

By Serdal Okur, Ph.D.

A thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at Virginia Commonwealth University.

Virginia Commonwealth University, 2014.

Major Director: Ümit Özgür, Associate Professor, Electrical and Computer Engineering

This thesis explores radiative efficiencies and recombination dynamics in InGaN-based heterostructures and their applications as active regions in blue light emitters and particularly vertical cavities. The investigations focus on understanding the mechanism of efficiency loss at high injection as well as developing designs to mitigate …

Quantum Efficiency Enhancement For Gan Based Light-Emitting Diodes And Vertical Cavity Surface-Emitting Lasers, Fan Zhang

Theses and Dissertations

This thesis explores the improvement of quantum efficiencies for InGaN/GaN heterostructures and their applications in light-emitting diodes (LEDs) and vertical cavity surface-emitting lasers (VCSELs). Different growth approaches and structural designs were investigated to identify and address the major factors limiting the efficiency. (1) Hot electron overflow and asymmetrical electron/hole injection were found to be the dominant reasons for efficiency degradation in nitride LEDs at high injection; (2) delta p-doped InGaN quantum barriers were employed to improve hole concentration inside the active region and therefore improve hole injection without sacrificing the layer quality; (3) InGaN active regions based on InGaN multiple …

Enhancing Gan Led Efficiency Through Nano-Gratings And Standing Wave Analysis, Gabriel M. Halpin

Master's Theses

Improving energy efficient lighting is a necessary step in reducing energy consumption.Lighting currently consumes 17% of all U.S. residential and commercial electricity, but a report from the U.S. Office of Energy Efficiency and Renewable Energy projects that switching to LED lighting over the next 20 years will save 46% of electricity used in lighting.GaN LEDs are used for their efficient conversion of electricity to light, but improving GaN efficiency requires optically engineering the chip to extract more light.Total internal reflection limits GaN LED performance since light must approach the chip surface within 23.6° of normal to escape into air.This thesis …

Off Grid Solar Powered Street Light, Justin Fang, Billy Pham

Electrical Engineering

Street lights are fixtures found in every city and serve the important purpose of illuminating the streets and keeping the roads safe for pedestrians and drivers. Current street lights are powered by the grid, power which is paid for by the taxpayers and could have been used to power homes instead. With this project, our goal is to design and implement an electric power system that collects and stores solar energy, and delivers power to an LED smart street light. The resulting system would reduce street light energy costs by 100% since they would not draw any power from the …

Dislocation Reduction In Silicon Doped High Aluminum Content Algan Layers For Deep Uv Optoelectronic Devices, Hung-Chi Chen

Theses and Dissertations

III-Nitride based deep ultraviolet (UV) light emitting diodes (LEDs) are prospective candidates to replace the conventional bulky, expensive and environmentally harmful mercury lamp as new UV light sources, used in the applications of water and air purification, germicidal and biomedical instrumentation systems, etc. Due to the lack of native substrates and poor carrier injection, AlGaN-based deep UV LED is suffering from low optical power and low overall efficiency, which prevents the availability of low cost, high efficiency deep UV LED on the market.

This dissertation is focused on improving the efficiency of deep UV LEDs, by improving the base template …

Effects Of N-Type Doping On Algan Material Quality, Devendra Diwan

Theses and Dissertations

The field of group III-nitride semiconductors has seen incredible developments during last couple of decades. They are recognized as the most promising materials for a wide field of optoelectronics and electronic devices. Their bandgap ranges from 6.2 eV for AlN to 0.7 eV for InN, covering a wide spectral range from infrared (1.77 mm) to deep ultraviolet (200 nm). Their direct bandgap makes them useful for fabricating optoelectronic devices such as light emitting diodes (LEDs), laser diodes (LDs), and photodetectors. III-nitride semiconductor materials also possess strong bond strengths and exhibit good structural, chemical and thermal stability. These properties make it …

Solar Powered Led Lantern For Developing Countries, Lacy Billingsly Iii

Electrical Engineering

In recent years, both LED and solar technology have become the focus of sustainable energy. LED lighting uses significantly less power than its fluorescent competitor. Solar cells enable clean, natural, and portable power. As these two entities become more efficient at exponential rates, the hope for the wide use of off-grid lighting in less developed countries seemingly increases at the same rate. Currently, there has been a development of industry for portable solar powered lighting systems. Before designing a product, a study was conducted of current products on the market that aim to light dark homes. This study and design …

Programmable Household Led Light Fixture, Jordan Locano

Electrical Engineering

This report details the development and construction of a LED light fixture to be used for household lighting. This document details background information, design ideas, project specifications, production, assembly, testing, and conclusions involved with this project. The goals of this project is to design and build a cost-effective replacement for traditional room lighting that can perform better and last longer than traditional methods.

The Design And Manufacture Of A Light Emitting Diode Package For General Lighting, Michael S. Krist

Master's Theses

Lighting technologies have evolved over the years to become higher quality, more efficient sources of light. LEDs are poised to become the market standard for general lighting because they are the most power efficient form of lighting and do not contain hazardous materials. Unfortunately, LEDs pose unique problems because advanced thermal management is required to remove the high heat fluxes generated by such relatively small devices. These problems have already been overcome with complex packaging and exotic materials, but high costs are preventing this technology from displacing current lighting technologies.

The purpose of this study is to develop a low-cost …

Passivation Of Polymer Light-Emitting Diodes, Stephen A. Fehrman

Electrical Engineering

This senior project investigates various methods of packaging polymer LEDs. The polymer LEDs fabricated in the EE 422 Polymer Electronics lab use calcium cathodes. While calcium acts as an excellent low work function electrode, it quickly oxidizes in the presence of oxygen or water. Additionally, the intrusion of water can degrade the OC1C10-PPV electroluminescent polymer and the PEDOT polymer. Therefore, in order to use these devices outside the inert atmosphere of a glove box, we must first apply a passivation layer that inhibits the deterioration of these materials.

For this project I will test two packaging methods. The first method …

Incorporating Wireless Power Transfer In An Led Lighting Application, Jonathan S. Shipley

Theses and Dissertations

There are various situations in which electrical energy is desired but cannot by conveniently supplied. Since the days of Hienrich Hertz and Nikola Tesla, scientists have tried to solve this problem using different methods of wireless power transfer. Today, wireless power transfer has only been commercially demonstrated at small distances through use of induction. This thesis demonstrated the transfer of wireless power at relatively large distances through radio frequencies in the development of a prototype for a commercial product - a wireless household lamp.

Effects Of Neutron Radiation On Resonant Cavity Light-Emitting Diodes, Daniel S. Hinkel

Theses and Dissertations

Resonant Cavity Light Emitting Diodes (RCLEDs) were irradiated in Ohio State University's nuclear reactor to determine the effects of Neutron displacement damage. The RCLEDs were characterized both before and after irradiation by their current versus voltage curves (I-V curves) and external light power versus current curves (L-I curves). The I-V curves showed an increase in the "knee voltage" at a neutron fluence of 1.45x10¹⁷ neutrons/cm2. Logarithmic decreases in external light power and differential quantum efficiency were observed. Significant decreases in external light power were observed at neutron fluences greater than 5.1x10¹³ neutrons/cm². Equations were developed to …