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- All Subjects: engineering
- All Subjects: Materials Science
- Creators: Goryll, Michael
Description
The partially-depleted (PD) silicon Metal Semiconductor Field Effect Transistor (MESFET) is becoming more and more attractive for analog and RF applications due to its high breakdown voltage. Compared to conventional CMOS high voltage transistors, the silicon MESFET can be fabricated in commercial standard Silicon-on-Insulator (SOI) CMOS foundries without any change to the process. The transition frequency of the device is demonstrated to be 45GHz, which makes the MESFET suitable for applications in high power RF power amplifier designs. Also, high breakdown voltage and low turn-on resistance make it the ideal choice for switches in the switching regulator designs. One of the anticipated applications of the MESFET is for the pass device for a low dropout linear regulator. Conventional NMOS and PMOS linear regulators suffer from high dropout voltage, low bandwidth and poor stability issues. In contrast, the N-MESFET pass transistor can provide an ultra-low dropout voltage and high bandwidth without the need for an external compensation capacitor to ensure stability. In this thesis, the design theory and problems of the conventional linear regulators are discussed. N-MESFET low dropout regulators are evaluated and characterized. The error amplifier used a folded cascode architecture with gain boosting. The source follower topology is utilized as the buffer to sink the gate leakage current from the MESFET. A shunt-feedback transistor is added to reduce the output impedance and provide the current adaptively. Measurement results show that the dropout voltage is less than 150 mV for a 1A load current at 1.8V output. Radiation measurements were done for discrete MESFET and fully integrated LDO regulators, which demonstrate their radiation tolerance ability for aerospace applications.
ContributorsChen, Bo (Author) / Thornton, Trevor (Thesis advisor) / Bakkaloglu, Bertan (Committee member) / Goryll, Michael (Committee member) / Arizona State University (Publisher)
Created2013
Description
Carrier lifetime is one of the few parameters which can give information about the low defect densities in today's semiconductors. In principle there is no lower limit to the defect density determined by lifetime measurements. No other technique can easily detect defect densities as low as 10-9 - 10-10 cm-3 in a simple, contactless room temperature measurement. However in practice, recombination lifetime τr measurements such as photoconductance decay (PCD) and surface photovoltage (SPV) that are widely used for characterization of bulk wafers face serious limitations when applied to thin epitaxial layers, where the layer thickness is smaller than the minority carrier diffusion length Ln. Other methods such as microwave photoconductance decay (µ-PCD), photoluminescence (PL), and frequency-dependent SPV, where the generated excess carriers are confined to the epitaxial layer width by using short excitation wavelengths, require complicated configuration and extensive surface passivation processes that make them time-consuming and not suitable for process screening purposes. Generation lifetime τg, typically measured with pulsed MOS capacitors (MOS-C) as test structures, has been shown to be an eminently suitable technique for characterization of thin epitaxial layers. It is for these reasons that the IC community, largely concerned with unipolar MOS devices, uses lifetime measurements as a "process cleanliness monitor." However when dealing with ultraclean epitaxial wafers, the classic MOS-C technique measures an effective generation lifetime τg eff which is dominated by the surface generation and hence cannot be used for screening impurity densities. I have developed a modified pulsed MOS technique for measuring generation lifetime in ultraclean thin p/p+ epitaxial layers which can be used to detect metallic impurities with densities as low as 10-10 cm-3. The widely used classic version has been shown to be unable to effectively detect such low impurity densities due to the domination of surface generation; whereas, the modified version can be used suitably as a metallic impurity density monitoring tool for such cases.
ContributorsElhami Khorasani, Arash (Author) / Alford, Terry (Thesis advisor) / Goryll, Michael (Committee member) / Bertoni, Mariana (Committee member) / Arizona State University (Publisher)
Created2013
Description
Photodetectors in the 1.7 to 4.0 μm range are being commercially developed on InP substrates to meet the needs of longer wavelength applications such as thermal and medical sensing. Currently, these devices utilize high indium content metamorphic Ga1-xInxAs (x > 0.53) layers to extend the wavelength range beyond the 1.7 μm achievable using lattice matched GaInAs. The large lattice mismatch required to reach the extended wavelengths results in photodetector materials that contain a large number of misfit dislocations. The low quality of these materials results in a large nonradiative Shockley Read Hall generation/recombination rate that is manifested as an undesirable large thermal noise level in these photodetectors. This work focuses on utilizing the different band structure engineering methods to design more efficient devices on InP substrates. One prospective way to improve photodetector performance at the extended wavelengths is to utilize lattice matched GaInAs/GaAsSb structures that have a type-II band alignment, where the ground state transition energy of the superlattice is smaller than the bandgap of either constituent material. Over the extended wavelength range of 2 to 3 μm this superlattice structure has an optimal period thickness of 3.4 to 5.2 nm and a wavefunction overlap of 0.8 to 0.4, respectively. In using a type-II superlattice to extend the cutoff wavelength there is a tradeoff between the wavelength reached and the electron-hole wavefunction overlap realized, and hence absorption coefficient achieved. This tradeoff and the subsequent reduction in performance can be overcome by two methods: adding bismuth to this type-II material system; applying strain on both layers in the system to attain strain-balanced condition. These allow the valance band alignment and hence the wavefunction overlap to be tuned independently of the wavelength cutoff. Adding 3% bismuth to the GaInAs constituent material, the resulting lattice matched Ga0.516In0.484As0.970Bi0.030/GaAs0.511Sb0.489superlattice realizes a 50% larger absorption coefficient. While as, similar results can be achieved with strain-balanced condition with strain limited to 1.9% on either layer. The optimal design rules derived from the different possibilities make it feasible to extract superlattice period thickness with the best absorption coefficient for any cutoff wavelength in the range.
ContributorsSharma, Ankur R (Author) / Johnson, Shane (Thesis advisor) / Goryll, Michael (Committee member) / Roedel, Ronald (Committee member) / Arizona State University (Publisher)
Created2013
Description
The constant scaling of supply voltages in state-of-the-art CMOS processes has led to severe limitations for many analog circuit applications. Some CMOS processes have addressed this issue by adding high voltage MOSFETs to their process. Although it can be a completely viable solution, it usually requires a changing of the process flow or adding additional steps, which in turn, leads to an increase in fabrication costs. Si-MESFETs (silicon-metal-semiconductor-field-effect-transistors) from Arizona State University (ASU) on the other hand, have an inherent high voltage capability and can be added to any silicon-on-insulator (SOI) or silicon-on-sapphire (SOS) CMOS process free of cost. This has been proved at five different commercial foundries on technologies ranging from 0.5 to 0.15 μm. Another critical issue facing CMOS processes on insulated substrates is the scaling of the thin silicon channel. Consequently, the future direction of SOI/SOS CMOS transistors may trend away from partially depleted (PD) transistors and towards fully depleted (FD) devices. FD-CMOS are already being implemented in multiple applications due to their very low power capability. Since the FD-CMOS market only figures to grow, it is appropriate that MESFETs also be developed for these processes. The beginning of this thesis will focus on the device aspects of both PD and FD-MESFETs including their layout structure, DC and RF characteristics, and breakdown voltage. The second half will then shift the focus towards implementing both types of MESFETs in an analog circuit application. Aside from their high breakdown ability, MESFETs also feature depletion mode operation, easy to adjust but well controlled threshold voltages, and fT's up to 45 GHz. Those unique characteristics can allow certain designs that were previously difficult to implement or prohibitively expensive using conventional technologies to now be achieved. One such application which benefits is low dropout regulators (LDO). By utilizing an n-channel MESFET as the pass transistor, a LDO featuring very low dropout voltage, fast transient response, and stable operation can be achieved without an external capacitance. With the focus of this thesis being MESFET based LDOs, the device discussion will be mostly tailored towards optimally designing MESFETs for this particular application.
ContributorsLepkowski, William (Author) / Thornton, Trevor (Thesis advisor) / Bakkaloglu, Bertan (Committee member) / Goryll, Michael (Committee member) / Ayyanar, Raja (Committee member) / Arizona State University (Publisher)
Created2010
Description
This thesis presents a kit of materials intended to present students with a glimpse of what engineering entails by guiding them through building engineering projects similar to what is in the real world. The objective of this project is to pique the interest of children by introducing them to lesser known engineering related topics, and increasing their literacy of terms and methods engineers use to solve problems. The effectiveness of the kit’s content and teaching methods was tested in a classroom of 6th graders and was measured using the responses from surveys handed out. I found that kit did in fact positively lead to a change in the way the students perceived engineering, and it taught students about new engineering related topics. Students were capable of completing difficult tasks of wiring and coding successfully through the use of detailed instruction. However, the instructions were seen in two opposing views of either being too overwhelming or more guidance was necessary.
ContributorsQuezada, Hebellyn Arleth (Author) / Aukes, Daniel (Thesis director) / Kellam, Nadia (Committee member) / Engineering Programs (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
The relationship between video games and education is something that has been studied extensively in academia. Based upon these studies a new concept was created, gamification. Gamification is the next step in video game research to analyze why video games enhance learning. The interest and research into this concept have developed so much so that it has become its own topic area for research. This study is looking to analyze the effect that gamification has on not only learning, but also self-efficacy. Through a choose your own adventure game, the knowledge and self-efficacy of participants will be examined to observe the differences when learning difficult engineering concepts with and without gamification. It is expected that participants that experienced training through gamification will demonstrate deeper learning and higher self-efficacy than trained through a video. Furthermore, it is anticipated that some video trained participants’ self-efficacy will increase; however, their comprehension will be less than participants trained through gamification. The results of this study can help promote the interest in researching gamification and education, while influencing educators to corporate gamification elements when designing their courses. Moreover, this study continued through adaptation and integration into a statics forces class, investigated if the same results can be found within a classroom setting.
ContributorsKanechika, Amber (Author) / Craig, Scotty (Thesis director) / Roscoe, Rod (Committee member) / Engineering Programs (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
The purpose of this study is to spark a discussion for engineers and their firms to consider the impact of border barriers on wildlife. The focus of this study is to consider if or how engineers make those considerations, such as through design modifications. Barriers block wildlife migration patterns, disabling them from life-sustaining resources. This is particularly important due to an increasing trend in habitat loss, urban development, and climate change. During literature analysis of border barrier impacts, and outreaching to relevant organizations and individuals, there was little to no public documentation or discussion from the engineering community found. Discussion that was found is included in this study, but the lack of connection between conservation and engineering professionals is eminently profound. Therefore, the analysis of studying engineering design considerations additionally studied the relationship between environmental and engineering professionals. Types of research included involves literature analysis of journal articles, reports, project plans for construction, and environmental laws pertinent to wildlife impact.
ContributorsMcMillin, Kaci (Author) / Karwat, Darshan (Thesis director) / Senko, Jesse (Committee member) / Engineering Programs (Contributor) / Environmental and Resource Management (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
This creative project is a children’s book designed to teach young readers about engineering through a fictional story about a group of children creating a robot for their school’s show-and-tell. The story aims to teach engineering principles to children in a lighthearted and entertaining form, narrating notions such as the design process, prototyping, specialty fields, and repurposing. Other principles such as learning patience, compromise and teamwork are also conveyed throughout the plot details. Small life lessons that transcend the realm of engineering are also embodied throughout. The plot of the story is a young girl who goes to visit her grandfather who is a garage tinkerer with a love of spare parts. He tells her about his job as a robotics engineer, and she loves it. She goes and tells her friends who decide they want to make a robot for show-and-tell at school. The grandfather agrees to help them build a robot and thus the group of kids are walked through the engineering design process, learning new things (and specialization) along the way. The story ends by revealing that the whole story was a flashback the main character was having as she is about to start her first day at an engineering firm.
ContributorsReed, Shelby Marie (Author) / Oberle, Eric (Thesis director) / Williams, Wendy (Committee member) / Engineering Programs (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
With the ongoing development of simulation technology, classic barriers to social interactions are beginning to be dismantled. One such exchange is encapsulated within education—instructors can use simulations to make difficult topics more manageable and accessible to students. Within simulations that include virtual humans, however, there are important factors to consider. Participants playing in virtual environments will act in a way that is consistent with their real-world behaviors—including their implicit biases. The current study seeks to determine the impact of virtual humans’ skin tone on participants’ behaviors when applying engineering concepts to simulated projects. Within a comparable study focused on a medical training simulation, significantly more errors and delays were made when working for the benefit of dark-skinned patients in a virtual context. In the current study, participants were given a choose-your-own-adventure style game in which they constructed simulated bridges for either a light- ordark-skinned community, and the number of errors and time taken for each decision was tracked. Results are expected to be consistent with previous study, indicating a higher number of errors and less time taken for each decision, although these results may be attenuated by a
lack of time pressure and urgency to the given situations. If these expected results hold, there may be implications for both undergraduate engineering curriculum and real-world engineering endeavors.
lack of time pressure and urgency to the given situations. If these expected results hold, there may be implications for both undergraduate engineering curriculum and real-world engineering endeavors.
ContributorsEldemire, Kate (Author) / Craig, Scotty D. (Thesis director) / Roscoe, Rod D. (Committee member) / Engineering Programs (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
All around the automotive industry, the chassis dynamometer exists in a variety of configurations but all function to provide one common goal. The underlying goal is to measure a vehicle’s performance by measuring torque output and taking that measurement to calculate horsepower. This data is crucial in situations of testing development vehicles or for tuning heavily modified vehicles. While the current models in the industry serve their purposes for what they were intended to do, in theory, an additional system can be introduced to the dyno to render the system into an electric generator.
The hardware will consist of electric motors functioning as a generator by reversing the rotation of the motor (regenerative braking). Using the dynamometer with the additional motor system paired with a local battery, the entire system can be run off by their tuning service. When considering the Dynojet and Dynapack dynamometer, it was calculated that an estimated return of 81.5% of electricity used can be generated. Different factors such as how frequent the dyno is used and for how long affect the savings. With a generous estimate of 6 hours dyno run time a day for 250 business days and the cost of electricity being 13.19 cents/kwh the Dynapack came out to $326.45 a year and $1424.52 for the Dynojet. With the return of electricity, the amount saved comes out to $266.18 for the Dynapack and $1161.50 for the Dynojet. This will alleviate electrical costs dramatically in the long term allowing for performance shops to invest their saved money into more tools and equipment.
The hardware will consist of electric motors functioning as a generator by reversing the rotation of the motor (regenerative braking). Using the dynamometer with the additional motor system paired with a local battery, the entire system can be run off by their tuning service. When considering the Dynojet and Dynapack dynamometer, it was calculated that an estimated return of 81.5% of electricity used can be generated. Different factors such as how frequent the dyno is used and for how long affect the savings. With a generous estimate of 6 hours dyno run time a day for 250 business days and the cost of electricity being 13.19 cents/kwh the Dynapack came out to $326.45 a year and $1424.52 for the Dynojet. With the return of electricity, the amount saved comes out to $266.18 for the Dynapack and $1161.50 for the Dynojet. This will alleviate electrical costs dramatically in the long term allowing for performance shops to invest their saved money into more tools and equipment.
ContributorsCrisostomo, Ryan-Xavier Eddie (Author) / Contes, James (Thesis director) / Wishart, Jeffrey (Committee member) / Engineering Programs (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05