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Description
Gallium Nitride (GaN) is uniquely suited for Radio Frequency (RF) and power electronic applications due to its intrinsically high saturation velocity and high mobility compared to Silicon and Silicon Carbide (SiC). High Electron Mobility Transistors (HEMTs) have remained the primary topology for GaN transistors in RF applications. However, GaN HEMTs suffer from a variety of issues such as current crowding, lack of enhancement mode (E-Mode) operation and non-linearity. These drawbacks slow the widespread adoption of GaN devices for ultra-low voltage (ULV) applications such as voltage regulators, automotive and computing applications. E-mode operation is especially desired in low-voltage high frequency switching applications. In this context, Fin Field Effect Transistors (FinFETs) offer an alternative topology for ULV applications as opposed to conventional HEMTs. Recent advances in material processing, high aspect ratio epitaxial growth and etching methods has led to an increased interest in 3D nanostructures such as Nano-FinFETs and Nanowire FETs. A typical 3D nano-FinFET is the AlGaN/GaN Metal Insulator Semiconductor (MIS) FET wherein a layer of Al2O3 surrounds the AlGaN/GaN fin. The presence of the side gates leads to additional lateral confinement of the 2D Electron Gas (2DEG). Theoretical calculations of transport properties in confined systems such as AlGaN/GaN Finfets are scarce compared to those of their planar HEMT counterparts.
A novel simulator is presented in this dissertation, which employs self-consistent solution of the coupled 1D Boltzmann – 2D Schrödinger – 3D Poisson problem, to yield the channel electrostatics and the low electric field transport characteristics of AlGaN/GaN MIS FinFETs. The low field electron mobility is determined by solving the Boltzmann transport equation in the Quasi-1D region using 1D Ensemble Monte Carlo method. Three electron-phonon scattering mechanisms (acoustic, piezoelectric and polar optical phonon scattering) and interface roughness scattering at the AlGaN/GaN interface are considered in this theoretical model. Simulated low-field electron mobility and its temperature dependence are in agreement with experimental data reported in the literature.
A quasi-1D version of alloy clustering model is derived and implemented and the limiting effect of alloy clustering on the low-field electron mobility is investigated for the first time for MIS FinFET device structures.
ContributorsKumar, Viswanathan Naveen (Author) / Vasileska, Dragica (Thesis advisor) / Goodnick, Stephen (Committee member) / Nemanich, Robert (Committee member) / Povolotskyi, Michael (Committee member) / Esqueda, Ivan Sanchez (Committee member) / Arizona State University (Publisher)
Created2022
Description
The advent of silicon, germanium, narrow-gap III-V materials, and later the wide bandgap (WBG) semiconductors, and their subsequent revolution and enrichment of daily life begs the question: what is the next generation of semiconductor electronics poised to look like? Ultrawide bandgap (UWBG) semiconductors are the class of semiconducting materials that possess an electronic bandgap (EG) greater than that of gallium nitride (GaN), which is 3.4 eV. They currently consist of beta-phase gallium oxide (β-Ga2O3 ; EG = 4.6–4.9 eV), diamond (EG = 5.5 eV), aluminum nitride (AlN; EG =6.2 eV), cubic boron nitride (BN; EG = 6.4 eV), and other materials hitherto undiscovered. Such a strong emphasis is placed on the semiconductor bandgap because so many relevant electronic performance properties scale positively with the bandgap. Where power electronics is concerned, the Baliga's Figure of Merit (BFOM) quantifies how much voltage a device can block in the off state and how high its conductivity is in the on state. The BFOM has a sixth-order dependence on the bandgap. The UWBG class of semiconductors also possess the potential for higher switching efficiencies and power densities and better suitability for deep-UV and RF optoelectronics. Many UWBG materials have very tight atomic lattices and high displacement energies, which makes them suitable for extreme applications such as radiation-harsh environments commonly found in military, industrial, and outer space applications. In addition, the UWBG materials also show promise for applications in quantum information sciences. For all the inherent promise and burgeoning research efforts, key breakthroughs in UWBG research have only occurred as recently as within the last two to three decades, making them extremely immature in comparison with the well-known WBG materials and others before them. In particular, AlN suffers from a lack of wide availability of low-cost, highquality substrates, a stark contrast to β-Ga2O3, which is now readily commercially available. In order to realize more efficient and varied devices on the relatively nascent UWBG materials platform, a deeper understanding of the various devices and physics is necessary. The following thesis focuses on the UWBG materials AlN and β-Ga2O3, overlooking radiation studies, a novel device heterojunction, and electronic defect study.
ContributorsMontes, Jossue (Author) / Zhao, Yuji (Thesis advisor) / Vasileska, Dragica (Committee member) / Goodnick, Stephen (Committee member) / Sanchez Esqueda, Ivan (Committee member) / Arizona State University (Publisher)
Created2021
Description
As the single-junction silicon solar cell is approaching its theoretical efficiency limits, the loss from shading and resistance is gaining increasing attention. The metal grid pattern may cause an efficiency loss up to 1–3%abs (absolute percentage) depending on the grid’s materials and structure.Many attempts have been proposed to reduce the loss caused by the contacts and module. Among them, the monolithic solar cell, which is a solar cell with multiple string cells on the same wafer and connected in a series, presents advantages of low output current, busbar-free contact, minimized interconnection space, and ohmic loss reduction. However, this structure also introduces a lateral forward bias current through the base region, which severely degrades the cell’s performance. In addition, this interconnection in the base region has partially shunted certain solar cells in the monolithic cell, which created a mismatch between string cells.
For the last few decades, researchers have used different methods such as etching trenches or enlarging the distance between the neighboring string cells to solve this problem. However, these methods were both ineffective and defective.
In this work, a novel method of suppressing the lateral forward bias current is proposed. By adding a very high surface recombination to the mid-region between the string cells, the carrier density in the mid-region can be decreased close to the doping density. Thus, the resistivity in the mid-region can be increased tenfold or more. As a result, the lateral forward bias current is greatly reduced.
Other methods to reduce lateral forward bias current include optimizing the width of the mid-region, shading the mid-region, reducing the base doping and base thickness which can be used to reduce the mismatch as well.
Another method has been proposed to calculate the minimum efficiency loss of a monolithic cell compared to the baseline solar cell. As a result, the monolithic cell could potentially gain more advantages over the baseline solar cells with a thinner and low-doped wafer.
A monolithic solar cell with innovative designs is presented in this work which shows an efficiency that is potentially higher than that of normal solar cells.
ContributorsXue, Shujian (Author) / Bowden, Studart (Thesis advisor) / Goodnick, Stephen (Committee member) / Vasileska, Dragica (Committee member) / Goryll, Michael (Committee member) / Arizona State University (Publisher)
Created2022
Description
Linear bipolar circuits, designed with bipolar junction transistors (BJTs), are particularly vulnerable to the effects of space radiation. These circuits, which are usually commercial off-the-shelf (COTS) components, typically exhibit Enhanced Low Dose Rate Sensitivity (ELDRS), which is characterized by the enhancement of degradation when parts are exposed to radiation at low dose rates as compared to high dose rates. This phenomenon poses significant problems for the qualification of bipolar parts for use in low dose rate environments, such as most Earth orbits. ELDRS in BJTs has been well-documented in ground-based experiments; however, the effects of low dose rate irradiation on bipolar transistors manufactured in an integrated linear process had never been characterized in space - until the ELDRS experiment was launched in June 2019. The ELDRS instrument measures changes in the active collector and base currents in 24 lateral PNP (LPNP) BJTs on eight packaged die (three BJTs per die). Sixteen of the 24 BJTs are gated, while eight are standard, un-gated LPNPs. Device Under Test (DUT) and measurement variables include oxide thickness, passivation layer, packaging conditions, and gate voltage. This thesis reports the results obtained after more than 20 months of space flight in a highly elliptical Earth orbit. These results demonstrate that this category of bipolar devices is susceptible to low dose rate exposures and therefore exhibits the ELDRS effect in an actual space environment. This thesis also assess the impact of packaging variables on radiation response and examines one of the major causes behind radiation degradation, interface traps. An understanding of radiation effects in real space environments is critical for future missions that use these low-cost COTS bipolar technologies, making these results highly relevant for the satellite community.
ContributorsBenedetto, Adalin (Author) / Barnaby, Hugh J (Thesis advisor) / Goodnick, Stephen (Committee member) / Sanchez, Ivan (Committee member) / Arizona State University (Publisher)
Created2023
Description
Wide Bandgap (WBG) semiconductor materials are shaping day-to-day technologyby introducing powerful and more energy responsible devices. These materials have
opened the door for building basic semiconductor devices which are superior in terms of
handling high voltages, high currents, power, and temperature which is not possible using
conventional silicon technology. As the research continues in the field of WBG based
devices, there is a potential chance that the power electronics industry can save billions of
dollars deploying energy-efficient circuits in high power conversion electronics. Diamond,
silicon carbide and gallium nitride are the top three contenders among which diamond can
significantly outmatch others in a variety of properties. However, diamond technology is
still in its early phase of development and there are challenges involved in many aspects of
processing a successful integrated circuit. The work done in this research addresses three
major aspects of problems related to diamond technology. In the first part, the applicability
of compact modeling and Technology Computer-Aided Design (TCAD) modeling
technique for diamond Schottky p-i-n diodes has been demonstrated. The compact model
accurately predicts AC, DC and nonlinear behavior of the diode required for fast circuit
simulation. Secondly, achieving low resistance ohmic contact onto n-type diamond is one
of the major issues that is still an open research problem as it determines the performance
of high-power RF circuits and switching losses in power converters circuits. So, another
portion of this thesis demonstrates the achievement of very low resistance ohmic contact
(~ 10-4 Ω⋅cm2) onto n-type diamond using nano crystalline carbon interface layer. Using
the developed TCAD and compact models for low resistance contacts, circuit level
predictions show improvements in RF performance. Lastly, an initial study of breakdown
characteristics of diamond and cubic boron nitride heterostructure is presented. This study
serves as a first step for making future transistors using diamond and cubic boron nitride –
a very less explored material system in literature yet promising for extreme circuit
applications involving high power and temperature.
ContributorsJHA, VISHAL (Author) / Thornton, Trevor (Thesis advisor) / Goodnick, Stephen (Committee member) / Nemanich, Robert (Committee member) / Alford, Terry (Committee member) / Hoque, Mazhar (Committee member) / Arizona State University (Publisher)
Created2023
Description
An efficient thermal solver is available in the CMC that allows modeling self-heating in the electrical simulations, which treats phonons as flux and solves the energy balance equation to quantify thermal effects. Using this solver, thermal simulations were performed on GaN-HEMTs in order to test effect of gate architectures on the DC and RF performance of the device. A Π- gate geometry is found to suppress 19.75% more hot electrons corresponding to a DC power of 2.493 W/mm for Vgs = -0.6V (max transconductance) with respect to the initial T-gate. For the DC performance, the output current, Ids is nearly same for each device configuration over the entire bias range. For the RF performance, the current gain was evaluated over a frequency range 20 GHz to 120 GHz in each device for both thermal (including self-heating) and isothermal (without self-heating). The evaluated cutoff frequency is around 7% lower for the thermal case than the isothermal case. The simulated cutoff frequency closely follows the experimental cutoff frequency. The work was extended to the study of ultra-wide bandgap material (Diamond), where isotope effect causes major deterioration in thermal conductivity. In this case, bulk phonons are modeled as semiclassical particles solving the nonlinear Peierls - Boltzmann transport equation with a stochastic approach. Simulations were performed for 0.001% (ultra-pure), 0.1% and 1.07% isotope concentration (13C) of diamond, showing good agreement with the experimental values. Further investigation was performed on the effect of isotope on the dynamics of individual phonon branches, thermal conductivity and the mean free path, to identify the dominant phonon branch. Acoustic phonons are found to be the principal contributors to thermal conductivity across all isotope concentrations with transverse acoustic (TA2) branch is the dominant branch with a contribution of 40% at room temperature and 37% at 500K. Mean free path computations show the lower bound of device dimensions in order to obtain maximum thermal conductivity. At 300K, the lowest mean free path (which is attributed to Longitudinal Optical phonon) reduces from 24nm to 8 nm for isotope concentration of 0.001% and 1.07% respectively. Similarly, the maximum mean free path (which is attributed to Longitudinal Acoustic phonon) reduces from 4 µm to 3.1 µm, respectively, for the same isotope concentrations. Furthermore, PETSc (Portable, Extensible Toolkit for Scientific Computation) developed by Argonne National Lab, was included in the existing Cellular Monte Carlo device simulator as a Poisson solver to further extend the capability of the simulator. The validity of the solver was tested performing 2D and 3D simulations and the results were compared with the well-established multigrid Poisson solver.
ContributorsAcharjee, Joy (Author) / Saraniti, Marco (Thesis advisor) / Goodnick, Stephen (Committee member) / Thornton, Trevor (Committee member) / Wang, Robert (Committee member) / Arizona State University (Publisher)
Created2024
Fill Factor Loss Mechanisms: Analysis and Basic Understanding in Silicon Hetero-junction Solar Cells
Description
The objective of this thesis is to achieve a detailed understanding of the loss mechanisms in SHJ solar cells. The working principles of these cells and what affects the cell operation, e.g. the IV characteristics at the maximum power point (MPP) and the correspondingly ll factor (FF) are investigated. Dierent loss sources are analyzed separately, and the weight of each in the total loss at the MPP are evaluated. The total series resistance is measured and then compared with the value obtained through summation over each of its components. In other words, series resistance losses due to recombination, vertical and lateral carrier transport, metalization, etc, are individually evaluated, and then by adding all these components together, the total loss is calculated. The concept of ll factor and its direct dependence on the loss mechanisms at the MPP of the device is explained, and its sensitivity to nearly every processing step of the cell fabrication is investigated. This analysis provides a focus lens to identify the main source of losses in SHJ solar cells and pave the path for further improvements in cell efficiency.
In this thesis, we provide a detailed understanding of the FF concept; we explain how it can be directly measured; how it can be calculated and what expressions can better approximate its value and under what operating conditions. The relation between FF and cell operating condition at the MPP is investigated. We separately analyzed the main FF sources of losses including recombination, sheet resistance, contact resistance and metalization. We study FF loss due to recombination and its separate components which include the Augur, radiative and SRH recombination is investigated. We study FF loss due to contact resistance and its separate components which include the contact resistance of dierent interfaces, e.g. between the intrinsic and doped a-Si layers, TCO and a-Si layers. We also study FF loss due to lateral transport and its components that including the TCO sheet resistance, the nger and the busbars resistances.
In this thesis, we provide a detailed understanding of the FF concept; we explain how it can be directly measured; how it can be calculated and what expressions can better approximate its value and under what operating conditions. The relation between FF and cell operating condition at the MPP is investigated. We separately analyzed the main FF sources of losses including recombination, sheet resistance, contact resistance and metalization. We study FF loss due to recombination and its separate components which include the Augur, radiative and SRH recombination is investigated. We study FF loss due to contact resistance and its separate components which include the contact resistance of dierent interfaces, e.g. between the intrinsic and doped a-Si layers, TCO and a-Si layers. We also study FF loss due to lateral transport and its components that including the TCO sheet resistance, the nger and the busbars resistances.
ContributorsLeilaeioun, Mohammadmehdi (Ashling) (Author) / Goodnick, Stephen (Thesis advisor) / Goryll, Michael (Thesis advisor) / Bertoni, Mariana (Committee member) / Bowden, Stuart (Committee member) / Stuckelberger, Michael (Committee member) / Arizona State University (Publisher)
Created2018
Description
Achieving high efficiency in solar cells requires optimal photovoltaics materials for light absorption and as with any electrical device—high-quality contacts. Essentially, the contacts separate the charge carriers—holes at one terminal and electrons at the other—extracting them to an external circuit. For this purpose, the development of passivating and carrier-selective contacts that enable low interface defect density and efficient carrier transport is critical for making high-efficiency solar cells. The recent record-efficiency n-type silicon cells with hydrogenated amorphous silicon (a-Si:H) contacts have demonstrated the usefulness of passivating and carrier-selective contacts. However, the use of a-Si:H contacts should not be limited in just n-type silicon cells.
In the present work, a-Si:H contacts for crystalline silicon and cadmium telluride (CdTe) solar cells are developed. First, hydrogen-plasma-processsed a-Si:H contacts are used in n-type Czochralski silicon cell fabrication. Hydrogen plasma treatment is used to increase the Si-H bond density of a-Si:H films and decrease the dangling bond density at the interface, which leads to better interface passivation and device performance, and wider temperature-processing window of n-type silicon cells under full spectrum (300–1200 nm) illumination. In addition, thickness-varied a-Si:H contacts are studied for n-type silicon cells under the infrared spectrum (700–1200 nm) illumination, which are prepared for silicon-based tandem applications.
Second, the a-Si:H contacts are applied to commercial-grade p-type silicon cells, which have much lower bulk carrier lifetimes than the n-type silicon cells. The approach is using gettering and bulk hydrogenation to improve the p-type silicon bulk quality, and then applying a-Si:H contacts to enable excellent surface passivation and carrier transport. This leads to an open-circuit voltage of 707 mV in p-type Czochralski silicon cells, and of 702 mV, the world-record open-circuit voltage in p-type multi-crystalline silicon cells.
Finally, CdTe cells with p-type a-Si:H hole-selective contacts are studied. As a proof of concept, p-type a-Si:H contacts enable achieving the highest reported open-circuit voltages (1.1 V) in mono-crystalline CdTe devices. A comparative study of applying p-type a-Si:H contacts in poly-crystalline CdTe solar cells is performed, resulting in absolute voltage gain of 53 mV over using the standard tellurium contacts.
In the present work, a-Si:H contacts for crystalline silicon and cadmium telluride (CdTe) solar cells are developed. First, hydrogen-plasma-processsed a-Si:H contacts are used in n-type Czochralski silicon cell fabrication. Hydrogen plasma treatment is used to increase the Si-H bond density of a-Si:H films and decrease the dangling bond density at the interface, which leads to better interface passivation and device performance, and wider temperature-processing window of n-type silicon cells under full spectrum (300–1200 nm) illumination. In addition, thickness-varied a-Si:H contacts are studied for n-type silicon cells under the infrared spectrum (700–1200 nm) illumination, which are prepared for silicon-based tandem applications.
Second, the a-Si:H contacts are applied to commercial-grade p-type silicon cells, which have much lower bulk carrier lifetimes than the n-type silicon cells. The approach is using gettering and bulk hydrogenation to improve the p-type silicon bulk quality, and then applying a-Si:H contacts to enable excellent surface passivation and carrier transport. This leads to an open-circuit voltage of 707 mV in p-type Czochralski silicon cells, and of 702 mV, the world-record open-circuit voltage in p-type multi-crystalline silicon cells.
Finally, CdTe cells with p-type a-Si:H hole-selective contacts are studied. As a proof of concept, p-type a-Si:H contacts enable achieving the highest reported open-circuit voltages (1.1 V) in mono-crystalline CdTe devices. A comparative study of applying p-type a-Si:H contacts in poly-crystalline CdTe solar cells is performed, resulting in absolute voltage gain of 53 mV over using the standard tellurium contacts.
ContributorsShi, Jianwei (Author) / Holman, Zachary (Thesis advisor) / Bowden, Stuart (Committee member) / Bertoni, Mariana (Committee member) / Goodnick, Stephen (Committee member) / Arizona State University (Publisher)
Created2018
Description
Gallium Nitride (GaN) based Current Aperture Vertical Electron Transistors (CAVETs) present many appealing qualities for applications in high power, high frequency devices. The wide bandgap, high carrier velocity of GaN make it ideal for withstanding high electric fields and supporting large currents. The vertical topology of the CAVET allows for more efficient die area utilization, breakdown scaling with the height of the device, and burying high electric fields in the bulk where they will not charge interface states that can lead to current collapse at higher frequency.
Though GaN CAVETs are promising new devices, they are expensive to develop due to new or exotic materials and processing steps. As a result, the accurate simulation of GaN CAVETs has become critical to the development of new devices. Using Silvaco Atlas 5.24.1.R, best practices were developed for GaN CAVET simulation by recreating the structure and results of the pGaN insulated gate CAVET presented in chapter 3 of [8].
From the results it was concluded that the best simulation setup for transfer characteristics, output characteristics, and breakdown included the following. For methods, the use of Gummel, Block, Newton, and Trap. For models, SRH, Fermi, Auger, and impact selb. For mobility, the use of GANSAT and manually specified saturation velocity and mobility (based on doping concentration). Additionally, parametric sweeps showed that, of those tested, critical CAVET parameters included channel mobility (and thus doping), channel thickness, Current Blocking Layer (CBL) doping, gate overlap, and aperture width in rectangular devices or diameter in cylindrical devices.
Though GaN CAVETs are promising new devices, they are expensive to develop due to new or exotic materials and processing steps. As a result, the accurate simulation of GaN CAVETs has become critical to the development of new devices. Using Silvaco Atlas 5.24.1.R, best practices were developed for GaN CAVET simulation by recreating the structure and results of the pGaN insulated gate CAVET presented in chapter 3 of [8].
From the results it was concluded that the best simulation setup for transfer characteristics, output characteristics, and breakdown included the following. For methods, the use of Gummel, Block, Newton, and Trap. For models, SRH, Fermi, Auger, and impact selb. For mobility, the use of GANSAT and manually specified saturation velocity and mobility (based on doping concentration). Additionally, parametric sweeps showed that, of those tested, critical CAVET parameters included channel mobility (and thus doping), channel thickness, Current Blocking Layer (CBL) doping, gate overlap, and aperture width in rectangular devices or diameter in cylindrical devices.
ContributorsWarren, Andrew (Author) / Vasileska, Dragica (Thesis advisor) / Goodnick, Stephen (Committee member) / Zhao, Yuji (Committee member) / Arizona State University (Publisher)
Created2019
Description
Wide bandgap (WBG) semiconductors GaN (3.4 eV), Ga2O3 (4.8 eV) and AlN (6.2 eV), have gained considerable interests for energy-efficient optoelectronic and electronic applications in solid-state lighting, photovoltaics, power conversion, and so on. They can offer unique device performance compared with traditional semiconductors such as Si. Efficient GaN based light-emitting diodes (LEDs) have increasingly displaced incandescent and fluorescent bulbs as the new major light sources for lighting and display. In addition, due to their large bandgap and high critical electrical field, WBG semiconductors are also ideal candidates for efficient power conversion.
In this dissertation, two types of devices are demonstrated: optoelectronic and electronic devices. Commercial polar c-plane LEDs suffer from reduced efficiency with increasing current densities, knowns as “efficiency droop”, while nonpolar/semipolar LEDs exhibit a very low efficiency droop. A modified ABC model with weak phase space filling effects is proposed to explain the low droop performance, providing insights for designing droop-free LEDs. The other emerging optoelectronics is nonpolar/semipolar III-nitride intersubband transition (ISBT) based photodetectors in terahertz and far infrared regime due to the large optical phonon energy and band offset, and the potential of room-temperature operation. ISBT properties are systematically studied for devices with different structures parameters.
In terms of electronic devices, vertical GaN p-n diodes and Schottky barrier diodes (SBDs) with high breakdown voltages are homoepitaxially grown on GaN bulk substrates with much reduced defect densities and improved device performance. The advantages of the vertical structure over the lateral structure are multifold: smaller chip area, larger current, less sensitivity to surface states, better scalability, and smaller current dispersion. Three methods are proposed to boost the device performances: thick buffer layer design, hydrogen-plasma based edge termination technique, and multiple drift layer design. In addition, newly emerged Ga2O3 and AlN power electronics may outperform GaN devices. Because of the highly anisotropic crystal structure of Ga2O3, anisotropic electrical properties have been observed in Ga2O3 electronics. The first 1-kV-class AlN SBDs are demonstrated on cost-effective sapphire substrates. Several future topics are also proposed including selective-area doping in GaN power devices, vertical AlN power devices, and (Al,Ga,In)2O3 materials and devices.
In this dissertation, two types of devices are demonstrated: optoelectronic and electronic devices. Commercial polar c-plane LEDs suffer from reduced efficiency with increasing current densities, knowns as “efficiency droop”, while nonpolar/semipolar LEDs exhibit a very low efficiency droop. A modified ABC model with weak phase space filling effects is proposed to explain the low droop performance, providing insights for designing droop-free LEDs. The other emerging optoelectronics is nonpolar/semipolar III-nitride intersubband transition (ISBT) based photodetectors in terahertz and far infrared regime due to the large optical phonon energy and band offset, and the potential of room-temperature operation. ISBT properties are systematically studied for devices with different structures parameters.
In terms of electronic devices, vertical GaN p-n diodes and Schottky barrier diodes (SBDs) with high breakdown voltages are homoepitaxially grown on GaN bulk substrates with much reduced defect densities and improved device performance. The advantages of the vertical structure over the lateral structure are multifold: smaller chip area, larger current, less sensitivity to surface states, better scalability, and smaller current dispersion. Three methods are proposed to boost the device performances: thick buffer layer design, hydrogen-plasma based edge termination technique, and multiple drift layer design. In addition, newly emerged Ga2O3 and AlN power electronics may outperform GaN devices. Because of the highly anisotropic crystal structure of Ga2O3, anisotropic electrical properties have been observed in Ga2O3 electronics. The first 1-kV-class AlN SBDs are demonstrated on cost-effective sapphire substrates. Several future topics are also proposed including selective-area doping in GaN power devices, vertical AlN power devices, and (Al,Ga,In)2O3 materials and devices.
ContributorsFu, Houqiang (Author) / Zhao, Yuji (Thesis advisor) / Vasileska, Dragica (Committee member) / Goodnick, Stephen (Committee member) / Yu, Hongbin (Committee member) / Wang, Liping (Committee member) / Arizona State University (Publisher)
Created2019