Electronic Devices and Semiconductor Manufacturing Commons^™

Electron – Phonon Interaction In Multiple Channel Gan Based Hfets: Heat Management Optimization, Romualdo A. Ferreyra

Theses and Dissertations

New power applications for managing increasingly higher power levels require that more heat be removed from the power transistor channel. Conventional treatments for heat dissipation do not take into account the conversion of excess electron energy into longitudinal optical (LO) phonons, whose associated heat is stored in the channel unless such LO phonons decay into longitudinal acoustic (LA) phonons via a Ridley path. A two dimensional electron gas (2DEG) density of ~5×10¹²cm^-2 in the channel results in a strong plasmon–LO phonon coupling (resonance) and a minimum LO phonon lifetime is experimentally observed, implying fast heat removal from …

Measurement And Modeling Of Humidity Sensors, Jingbo Tong

Theses and Dissertations--Electrical and Computer Engineering

Humidity measurement has been increasingly important in many industries and process control applications. This thesis research focus mainly on humidity sensor calibration and characterization. The humidity sensor instrumentation is briefly described. The testing infrastructure was designed for sensor data acquisition, in order to compensate the humidity sensor’s temperature coefficient, temperature chambers using Peltier elements are used to achieve easy-controllable stable temperatures. The sensor characterization falls into a multivariate interpolation problem. Neuron networks is tried for non-linear data fitting, but in the circumstance of limited training data, an innovative algorithm was developed to utilize shape preserving polynomials in multiple planes in …

A Multi-Physics Computational Approach To Simulating Thz Photoconductive Antennas With Comparison To Measured Data And Fabrication Of Samples, Darren Ray Boyd

Theses and Dissertations--Electrical and Computer Engineering

The frequency demands of radiating systems are moving into the terahertz band with potential applications that include sensing, imaging, and extremely broadband communication. One commonly used method for generating and detecting terahertz waves is to excite a voltage-biased photoconductive antenna with an extremely short laser pulse. The pulsed laser generates charge carriers in a photoconductive substrate which are swept onto the metallic antenna traces to produce an electric current that radiates or detects a terahertz band signal. Therefore, analysis of a photoconductive antenna requires simultaneous solutions of both semiconductor physics equations (including drift-diffusion and continuity relations) and Maxwell’s equations. A …

Switched-Capacitor Voltage Doubler Design Using 0.5 Μm Technology, Hanfeng Wang

Theses

While integrated circuit (IC) power management has been an eternal topic for chip designers, inductor based DC-DC converters have been dominant in the field for years. However, because of the natures of inductors: large electro-magnetic interference, high coupling noise, and difficult silicon fabrication process, they are not favorable to on-chip solutions. Switched-capacitor (SC) DC-DC converters, which adopt capacitors for their energy storage components, have become increasingly popular among both the academia and the industry, because, apparently, they avoid the drawbacks of the inductor counterparts, and can be directly implemented on-chip without additional fabrication process.

In this paper, we will investigate …

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 …

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 …

Using Software-Based Decision Procedures To Control Instruction-Level Execution, William B. Kimball

AFIT Patents

An apparatus, method and program product are provided for securing a computer system. A digital signature of an application is checked, which is loaded into a memory of the computer system configured to contain memory pages. In response to finding a valid digital signature, memory pages containing instructions of the application are set as executable and memory pages other than those containing instructions of the application are set as non-executable. Instructions in executable memory pages are executed. Instructions in non-executable memory pages are prevented from being executed. A page fault is generated in response to an attempt to execute an …

Physical Design Of A Smart Camera With Integrated Digital Pixel Sensors Using A 0.13Μm 8-Layer Metal Cmos Process, Mahir K. Gharzai

Department of Electrical and Computer Engineering: Dissertations, Theses, and Student Research

The design of cameras has historically kept imagery and computational circuitry isolated in an attempt to maximize image quality by improving pixel pitch and routing density. Although this technique has worked in creating high density arrays of pixels for large resolution imagers, it has never been able to achieve high framerate computational operations.

A radical approach is introduced to solve this dilemma by creating compact, low- power pixel elements with built-in analog-to-digital converters that directly interface with digital logic. These pixels are capable of integrating alongside logic cells and to create an array of pixels inside the processor that can …

Investigation Of The Effects Of Rapid Thermal Annealing On Mbe Grown Gaasbi/Gaas Heterostructures For Optoelectronic Devices, Perry C. Grant

Graduate Theses and Dissertations

High efficiency optoelectronic devices rely on high quality materials making up the device structure. The scope of this thesis investigates the effectiveness of rapid thermal annealing (RTA) at improving the material quality of GaAsBi/GaAs heterostructures. During the fabrication of a device, the contacts of the device had the rapid thermal annealing process accomplished to produce ohmic contacts and this research explored if this annealing treatment degraded the quantum wells that made up the active region of a device. To investigate these effects, a system to measure the photoluminescence of the material system was constructed utilizing Fourier Transform Infrared Spectroscopy. The …

Zinc Oxide Nanorod Based Ultraviolet Detectors With Wheatstone Bridge Design, Arun Vasudevan

Graduate Theses and Dissertations

This research work, for the first time, investigated metal semiconductor-metal (MSM) zine oxide (ZnO) nanorod based ultra-violet (UV) detectors having a Wheatstone bridge design with a high

responsivity at room temperature and above, as well as a responsivity that was largely independent of the change in ambient conditions. The ZnO nanorods which acted as the sensing element of the detector were grown by a chemical growth technique. Studies were conducted to determine the effects on ZnO nanorod properties by varying the concentration of the chemicals used for the rod growth. These studies showed how the rod diameter and the deposition …

Design, Fabrication And Characterization Of Plasmonic Fishnet Structures For The Enhancement Of Absorption In Thin Film Solar Cells, Sayan Seal

Graduate Theses and Dissertations

Incorporating plasmonic structures into the back spacer layer of thin film solar cells (TFSCs) is an efficient way to improve their performance. The fishnet structure; which is a tunable, plasmonic light scatterer is used to enhance light absorption. Unlike other plasmonic particles that have been previously suggested, the fishnet is an electrically connected wire mesh and does not result in electric field localization, hence it results in greater absorption in the intrinsic Si layer. Unlike other designs, the fishnet structure is placed in the back spacer layer of the TFSC, so it does not block any incident light. There is …

Max Operation In Statistical Static Timing Analysis On The Non-Gaussian Variation Sources For Vlsi Circuits, Abu M. Baker

UNLV Theses, Dissertations, Professional Papers, and Capstones

As CMOS technology continues to scale down, process variation introduces significant uncertainty in power and performance to VLSI circuits and significantly affects their reliability. If this uncertainty is not properly handled, it may become the bottleneck of CMOS technology improvement. As a result, deterministic analysis is no longer conservative and may result in either overestimation or underestimation of the circuit delay. As we know that Static-Timing Analysis (STA) is a deterministic way of computing the delay imposed by the circuits design and layout. It is based on a predetermined set of possible events of process variations, also called corners of …

Role Of Atomic Variability In Dielectric Charging: A First-Principles-Based Multiscale Modeling Study, Ravi Pramod Kumar Vedula, Sambit Palit, Muhammad A. Alam, Alejandro Strachan

Birck and NCN Publications

We present a dielectric charging model that combinesab initiocalculations of trap levels with a continuum-level transport model and apply it to interpret charging currents in amorphous silicon nitride. Density functional theory calculations on an ensemble of structures predict a distribution of electron trap levels up to 1.8 eV below the conduction band edge and provide insight into the physical trapping mechanisms. Incorporating this information in the continuum model, as opposed to the standard approach of a single adjustable trap level, not only leads to a more accurate description of experimental current transients in metal-insulator-metal capacitors, but also to a more …

Mems Fabrication Process Base On Su-8 Masking Layers, Scott A. Ostrow, Ronald A. Coutu Jr.

AFIT Patents

A novel fabrication process uses a combination of negative and positive photoresists with positive tone photomasks, resulting in masking layers suitable for bulk micromachining high-aspect ratio microelectromechanical systems (MEMS) devices. This technique allows the use of positive photomasks with negative resists, opening the door to an ability to create complementary mechanical structures without the fabrication delays and costs associated with having to obtain a negative photomask. In addition, whereas an SU-8 mask would normally be left in place after processing, a technique utilizing a positive photoresist as a release layer has been developed so that the SU-8 masking material can …

Mems Lab Simulation Tool, Oluwatosin D. Adeosun, Sambit Palit, Ankit Jain, Muhammad A. Alam

The Summer Undergraduate Research Fellowship (SURF) Symposium

MEMS actuators have multiple design applications. Understanding their behavior as well as the ability to predict their actuation characteristics and voltage response is important when designing these actuators. In order to know these devices will behave, designers have to solve multiple analytical equations and experiments that can be very time consuming. Over the course of the summer a tool was created on nanoHUB that will allow users to enter information about a MEMS actuator and provide the voltage response of the actuator. To create the tool, scaling equations were first provided for various geometry configurations and the equations were next …

Assessing The Mvs Model For Nanotransistors, Siyang Liu, Xingshu Sun, Mark S. Lundstrom

The Summer Undergraduate Research Fellowship (SURF) Symposium

A simple semi-empirical compact MOSFET model has been developed, which is called MIT virtual source (MVS) model. Compare to other model used in industry, MVS model requires only a few parameters, most of which can be directly obtained from experiment, and produce accurate results. One aim of this paper is to test the applicability of the MVS model to transistor made from MoS₂ rather than silicon. Another target is to determine the sustainability of the MVS model under different transistor tests. To achieve these goals, the MVS model will be used to fit the experimental data on MoS_{2 …}

Thread Based Battery For Low Power E-Textile Applications, Pranav Laxmanan, Girish Chitnis, Rahim Rahimi, Babak Ziaie

The Summer Undergraduate Research Fellowship (SURF) Symposium

Textile electronic systems, or e-textiles, are on the rise but their utility is limited by its power demand. Potential applications include point-of-care diagnostic systems that would enable medical monitoring at the site of care. A small, inexpensive, and easy to use battery would enhance the capabilities of e-textile. Here we propose a thread based battery that attempts to satisfy these requirements. The thread based battery uses chemistry similar to an alkaline battery. The fabrication process involves patterning of current collector (silver epoxy or carbon ink) followed by zinc electroplating and manganese dioxide deposition. Thread present in between these two electrodes …

An Ant-Based Sensor Measurement Data Gathering System, Bolun Zhang, Dimitrios Peroulis

The Summer Undergraduate Research Fellowship (SURF) Symposium

Large-scale industries involved with a great amount of sensor measurements in their work are facing many challenges in data collection. Sensors are not on the same network; therefore each measurement has to be managed separately. Gathering all the measurement data to one terminal could be difficult. Once a measurement is obtained, it takes significant amount of time to process the data.The approaches our group takes here is to build a giant ANT wireless network that holds all the sensors’ measurements. To be more specific, every sensor has an ANT chip set up on its side. Each ANT chip is as …

Developing The Chargersat-1 Electrical Power System, Matt Rodencal

Von Braun Symposium Student Posters

No abstract provided.

A Novel Design Optimization Of A Fault-Tolerant Ac Permanent Magnet Machine-Drive System, Peng Zhang

Dissertations (1934 -)

In this dissertation, fault-tolerant capabilities of permanent magnet (PM) machines were investigated. The 12-slot 10-pole PM machines with V-type and spoke-type PM layouts were selected as candidate topologies for fault-tolerant PM machine design optimization problems. The combination of 12-slot and 10-pole configuration for PM machines requires a fractional-slot concentrated winding (FSCW) layout, which can lead to especially significant PM losses in such machines. Thus, a hybrid method to compute the PM losses was investigated, which combines computationally efficient finite-element analysis (CE-FEA) with a new analytical formulation for PM eddy-current loss computation in sine-wave current regulated synchronous PM machines. These algorithms …

Theoretical Analysis Of Laterally Vibrating Hammerhead Microcantilever Sensors In A Viscous Liquid, Jinjin Zhang

Dissertations (1934 -)

Dynamically driven prismatic microcantilevers excited in the in-plane flexural mode have been investigated and used in liquid-phase sensing applications. However, the performance is restricted due to their limited surface sensing area and higher stiffness in shorter and wider prismatic microcantilevers. To increase the surface sensing area, and further improve sensing characteristics, it has been proposed to investigate symmetric hammerhead microcantilevers vibrating laterally in viscous liquid media. In this work, a theoretical model is proposed and the characteristics of the microcantilevers with symmetric shaped hammerheads (isosceles trapezoid, semi-circle, uniform rectangle and composite rectangle) are investigated. In the analysis, the stem of …

Understanding Vehicular Traffic Behavior From Video: A Survey Of Unsupervised Approaches, Brendan Tran Morris, Mohan Manubhai Trivedi

Electrical & Computer Engineering Faculty Research

Recent emerging trends for automatic behavior analysis and understanding from infrastructure video are reviewed. Research has shifted from high-resolution estimation of vehicle state and instead, pushed machine learning approaches to extract meaningful patterns in aggregates in an unsupervised fashion. These patterns represent priors on observable motion, which can be utilized to describe a scene, answer behavior questions such as where is a vehicle going, how many vehicles are performing the same action, and to detect an abnormal event. The review focuses on two main methods for scene description, trajectory clustering and topic modeling. Example applications that utilize the behavioral modeling …

Metal-Assisted Etching Of Silicon Molds For Electroforming, Ralu Divan, Dan Rosenthal '14, Karim Ogando, Leonidas E. Ocola, Daniel Rosenmann, Nicolaie Moldovan

Student Publications & Research

Ordered arrays of high-aspect-ratio micro/nanostructures in semiconductors stirred a huge scientific interest due to their unique one-dimensional physical morphology and the associated electrical, mechanical, chemical, optoelectronic, and thermal properties. Metal-assisted chemical etching enables fabrication of such high aspect ratio Si nanostructures with controlled diameter, shape, length, and packing density, but suffers from structure deformation and shape inconsistency due to uncontrolled migration of noble metal structures during etching. Hereby the authors prove that a Ti adhesion layer helps in stabilizing gold structures, preventing their migration on the wafer surface while not impeding the etching. Based on this finding, the authors demonstrate …

Comprehensive Mapping And Benchmarking Of Esaki Diode Performance, David John Pawlik

Theses

The tunneling-FET (TFET) has been identified as a prospective MOSFET replacement technology with the potential to extend geometric and electrostatic scaling of digital integrated circuits. However, experimental demonstrations of the TFET have yet to reliably achieve drive currents necessary to power large scale integrated circuits. Consequentially, much effort has gone into optimizing the band-to-band tunneling (BTBT) efficiency of the TFET. In this work, the Esaki tunnel diode (ETD) is used as a short loop element to map and optimize BTBT performance for a large design space. The experimental results and tools developed for this work may be used to (1) …

Low Volume Dispensing With High Speed Dispensers, Sunny Agarwal

Graduate Dissertations and Theses

With the high pace of innovation in the semiconductor manufacturing industry, there has been an increasing demand for more energy efficient and environmental friendly products. This research relates to a complex process of fluid dispensing at low volumes on a printed circuit board. Currently, a more refined non-contact dispensing terminology named “Streaming” is widely used to stream out material at low volumes for various applications. The key solution is to frame a dispensing method that lends itself most closely to the requirements of a specific production process.

This study represents a detailed approach of dispensing low volumes of materials in …

High Voltage Direct Current Energy Transmission Using Modular Multilevel Converters, David Alejandro Guzman Pinzon

Graduate Theses and Dissertations

This thesis focus on high voltage direct current (HVdc) energy transmission using modular multilevel converter (MMC) based terminals. It provides a brief comparison between different HVdc technologies, focusing on voltage source converters (HVdc-VSC) with the MMC-based terminal emerging as the topology of choice for ratings less than 1 GW. The controllers for a two-terminal HVdc-link are analyzed and Matlab/Simulink^TM simulation models are presented. The simplified models and full Matlab/Simulink^TM based model are used to select the gains for the MMC controllers. Simulation results carried out on the full model validated the proposed methodologies. A new control technique that …

Electrical Design Considerations And Packaging Of Power Electronic Modules, Shijie Wang

Graduate Theses and Dissertations

A modern power electronic module can save significant energy usage in the power electronic systems by improving their switching efficiencies. One way to improve the efficiency of the power electronic module is to reduce its parasitic circuit elements. The purpose of this thesis is to investigate the mitigation of parasitic circuit elements in power electronic modules. General methods of mitigating parasitic inductances were analyzed by the Q3D Extractor and verified by the time-domain reflectometry (TDR) measurements. In most cases, the TDR measurement results closely matched those predicted by the Q3D Extractor. These methods were applied to design and analyze a …

Design And Fabrication Of Inverter And Rectifier Modules For Indirect Matrix Converter Applications, Saikishore Talakokkula

Graduate Theses and Dissertations

In power converter applications, silicon carbide (SiC) power semiconductor devices are preferred over their silicon counterparts due to many advantages such as wide bandgap, high junction temperatures and low on-state resistance. The SiC devices provide reduced conduction and switching losses. Due to the above mentioned advantages the power conversion efficiency of SiC devices is better compared to that of silicon (Si) devices.

This thesis studies the implementation of 1200V/17A Normally-off SiC JFETs for an indirect matrix converter (IMC) application. A discussion on the parasitic inductance optimization is presented based on the electromagnetic simulation results extracted from the Ansoft Q3D extractor. …

2-Dimensional Personal Motion Energy Harvester For Low Power Electronics, Manuel Gutierrez, Sean Scott, Dimitrios Peroulis

The Summer Undergraduate Research Fellowship (SURF) Symposium

In a lab, it becomes crucial to have a way to monitor that lab workers aren’t exposed to too much radiation. Such a device that detects this should have an energy harvester so that batteries aren’t required. The need for an energy harvester that generates power from a user’s movements in 2 dimensions is needed. This energy harvester is needed to power a radiation monitor. An energy harvester that generates power based off movements in 2 dimensions was developed. The energy harvester was created through a series of prototypes. Each prototype was built from a CAD drawing and a stereolithography …

Ferroelectric Batio3/Srtio3 Multilayered Thin Films For Room-Temperature Tunable Microwave Elements, Ming Liu, Chunrui Ma, Gregory Collins, Jian Liu, Chonglin Chen, Andy D. Alemayehu, Guru Subramanyam, Ying Ding, Jianghua Chen, Chao Dai, Yuan Lin, Melanie W. Cole

Electrical and Computer Engineering Faculty Publications

Ferroelectric BaTiO3/SrTiO3 with optimized c-axis-oriented multilayered thin films were epitaxially fabricated on (001) MgO substrates. The microstructural studies indicate that the in-plane interface relationships between the films as well as the substrate are determined to be (001)SrTiO3//(001)BaTiO3//(001)MgO and [100]SrTiO3//[100]BaTiO3//[100]MgO. The microwave (5 to 18 GHz) dielectric measurements reveal that the multilayered thin films have excellent dielectric properties with large dielectric constant, low dielectric loss, and high dielectric tunability, which suggests that the as-grown ferroelectric multilayered thin films can be developed for room-temperature tunable microwave elements and related device applications.