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1. A comparison of a commercial hydrodynamics TCAD solver and Fermi kinetics transport convergence for GaN HEMTs

Author

Tunga, Ashwin, Li, Kexin, Miller, Nicholas C., Grupen, Matt, Albrecht, John D., and Rakheja, Shaloo

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Various simulations of a GaN HEMT are used to study the behaviors of two different energy-transport models: the Fermi kinetics transport model and a hydrodynamics transport model as it is implemented in the device simulator Sentaurus from Synopsys. The electron transport and heat flow equations of the respective solvers are described in detail. The differences in the description of electron flux and the discretization methods are highlighted. Next, the transport models are applied to the same simulated device structure using identical meshes, boundary conditions, and material parameters. Static simulations show the numerical convergence of Fermi kinetics to be consistently quadratic or faster, whereas the hydrodynamic model is often sub-quadratic. Further comparisons of large signal transient simulations reveal the hydrodynamic model produces certain anomalous electron ensemble behaviors within the transistor structure. The fundamentally different electron dynamics produced by the two models suggest an underlying cause for their different numerical convergence characteristics.

Published
2022
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2. A W-Band GaN MMIC Single-Chip T/R Front End

Author

Sonnenberg, Timothy, Romano, Anthony, Miller, Nicholas C., and Popovic, Zoya

Abstract

A single-chip transmit–receive (T/R) front end covering (75–110) GHz is implemented in a 40-nm GaN on SiC HEMT process. The transmit path consists of a balanced power amplifier (PA) with three-stage unit PAs and an additional single-HEMT driver to achieve above 17-dB small-signal gain over the range and over 15 dB of large-signal gain across 75–108 GHz. The receive path consists of a three-stage low-noise amplifier (LNA) with a small-signal gain of 16–22 dB and de-embedded calculated noise figure (NF) of 4–6.5 dB across the range. A single pole double throw (SPDT) shunt switch with an insertion loss of 1–1.5 dB and an isolation between 15 and 20 dB across the band selects the transmit or receive paths in this half-duplex front end and does not show compression in transmit mode. In transmit mode, the front end measures >25 dBm over 75–110 GHz with a measured maximum of 29 dBm of output power at 92 GHz. In receive mode, the front end shows an NF of 5.2–7.8 dB with a gain of 16–22 dB. The demonstrated output power in transmit and NF in receive modes, with sufficient isolation, makes this single-die T/R component suitable for communications, imaging, and sensing.

Published
2024
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3. Isothermal Characterization of Traps in GaN HEMTs Operating in Class B Using a Real-Time Pulsed-RF NVNA Testbed

Author

Lindquist, Miles, Roblin, Patrick, Mikrut, Dominic, Nichols, Matthew J., and Miller, Nicholas C.

Abstract

This article presents a real-time nonlinear vector network analyzer (NVNA) testbed that enables the acquisition of the isothermal transient response of GaN HEMTs operating in pulsed class-B mode with arbitrary loads. An oscilloscope-based architecture and a cost-effective and traceable harmonic phase calibration procedure are presented for the proposed real-time NVNA. The system is configured to realize pulsed multiharmonic active load—pull (ALP) for synthesizing any class of operation. This real-time NVNA is used for the characterization of trapping in GaN HEMTs operating in pulsed class B under verified isothermal operation. It allows for the isothermal acquisition of the RF dynamic loadlines from pulse-to-pulse at different biasing conditions to account for different trapping states and operating temperatures. The capture and emission processes are monitored at each pulse using the quiescent current and RF power for each of the biasing conditions considered. These measurements and associated trap modeling demonstrate that a majority of the capture process is taking place in the first RF pulse (<200 ns) with the residual capture process distributed over various durations depending on the biasing condition and associated temperature. The proposed real-time NVNA combined with pulsed multiharmonic ALP should prove to be a useful tool for studying trapping effects in RF devices.

Published
2024
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4. Effect of High Temperature on the Performance of AlGaN/GaN T-Gate High-Electron Mobility Transistors With $\sim$140-nm Gate Length

Author

Islam, Ahmad E., primary, Sepelak, Nicholas P., additional, Miesle, Adam T., additional, Lee, Hanwool, additional, Snure, Michael, additional, Nikodemski, Stefan, additional, Walker, Dennis E., additional, Miller, Nicholas C., additional, Grupen, Matt, additional, Leedy, Kevin D., additional, Liddy, Kyle J., additional, Crespo, Antonio, additional, Hughes, Gary R., additional, Zhu, Wenjuan, additional, Poling, Brian, additional, Tetlak, Stephen, additional, Chabak, Kelson D., additional, and Green, Andrew J., additional

Published
2024
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6. A Discontinuous Galerkin Time Domain Framework for Periodic Structures Subject To Oblique Excitation

Author

Miller, Nicholas C., Baczewski, Andrew D., Albrecht, John D., and Shanker, Balasubramaniam

Subjects
Computer Science - Computational Engineering, Finance, and Science
Abstract

A nodal Discontinuous Galerkin (DG) method is derived for the analysis of time-domain (TD) scattering from doubly periodic PEC/dielectric structures under oblique interrogation. Field transformations are employed to elaborate a formalism that is free from any issues with causality that are common when applying spatial periodic boundary conditions simultaneously with incident fields at arbitrary angles of incidence. An upwind numerical flux is derived for the transformed variables, which retains the same form as it does in the original Maxwell problem for domains without explicitly imposed periodicity. This, in conjunction with the amenability of the DG framework to non-conformal meshes, provides a natural means of accurately solving the first order TD Maxwell equations for a number of periodic systems of engineering interest. Results are presented that substantiate the accuracy and utility of our method., Comment: Submitted to IEEE TAP on August 5th, 2013. Revision submitted on February 3rd, 2014

Published
2013
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7. The Rapid Analysis of Scattering from Periodic Dielectric Structures Using Accelerated Cartesian Expansions (ACE)

Author

Baczewski, Andrew D., Miller, Nicholas C., and Shanker, Balasubramaniam

Subjects
Physics - Computational Physics, Physics - Optics
Abstract

The analysis of fields in periodic dielectric structures arise in numerous applications of recent interest, ranging from photonic bandgap (PBG) structures and plasmonically active nanostructures to metamaterials. To achieve an accurate representation of the fields in these structures using numerical methods, dense spatial discretization is required. This, in turn, affects the cost of analysis, particularly for integral equation based methods, for which traditional iterative methods require O(N^2) operations, N being the number of spatial degrees of freedom. In this paper, we introduce a method for the rapid solution of volumetric electric field integral equations used in the analysis of doubly periodic dielectric structures. The crux of our method is the ACE algorithm, which is used to evaluate the requisite potentials in O(N) cost. Results are provided that corroborate our claims of acceleration without compromising accuracy, as well as the application of our method to a number of compelling photonics applications., Comment: 24 pages, 9 figures, submitted to JOSA A

Published
2011
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8. A Survey of GaN HEMT Technologies for Millimeter-Wave Low Noise Applications

Author

Miller, Nicholas C., primary, Arias-Purdue, Andrea, additional, Arkun, Erdem, additional, Brown, David, additional, Buckwalter, James F., additional, Coffie, Robert L., additional, Corrion, Andrea, additional, Denninghoff, Daniel J., additional, Elliott, Michael, additional, Fanning, Dave, additional, Gilbert, Ryan, additional, Green, Daniel S., additional, Herrault, Florian, additional, Heying, Ben, additional, King, Casey M., additional, Lam, Eythan, additional, Moon, Jeong-Sun, additional, Rowell, Petra V., additional, Siddiqi, Georges, additional, Smorchkova, Ioulia, additional, Tai, Joe, additional, Uyeda, Jansen, additional, and Wojtowicz, Mike, additional

Published
2023
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9. N-Polar GaN HEMTs in a High-Uniformity 100-mm Wafer Process With 43.6% Power-Added Efficiency and 2 W/mm at 94 GHz

Author

Arias-Purdue, Andrea, primary, Rowell, Petra V., additional, King, Casey M., additional, Carter, Andrew D., additional, Paniagua, Andres, additional, Shinohara, Keisuke, additional, Bergman, Josh, additional, Urteaga, Miguel E., additional, Miller, Nicholas C., additional, Elliott, Michael, additional, Gilbert, Ryan, additional, Herrault, Florian, additional, Green, Daniel, additional, and Buckwalter, James F., additional

Published
2023
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12. W-band fully passivated AlN/GaN HEMT device with 56% power-added efficiency and 780 mW/mm output power density at 94 GHz

Author

Arkun, F. Erdem, primary, Denninghoff, Dan, additional, Tran, Haidang, additional, Tran, Ryan, additional, Miller, Nicholas C., additional, Elliott, Michael, additional, Gilbert, Ryan, additional, Milosavljevic, Ivan, additional, Siddiqi, Georges, additional, Fireman, Micha, additional, Corrion, Andrea L., additional, Fanning, David, additional, Peterson, Christi, additional, Getter, Ariel, additional, and Clapper, Andrew, additional

Published
2023
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14. Effect of High Temperature on the Performance of AlGaN/GaN T-Gate High-Electron Mobility Transistors With ~140-nm Gate Length

Author

Islam, Ahmad E., Sepelak, Nicholas P., Miesle, Adam T., Lee, Hanwool, Snure, Michael, Nikodemski, Stefan, Walker, Dennis E., Miller, Nicholas C., Grupen, Matt, Leedy, Kevin D., Liddy, Kyle J., Crespo, Antonio, Hughes, Gary R., Zhu, Wenjuan, Poling, Brian, Tetlak, Stephen, Chabak, Kelson D., and Green, Andrew J.

Abstract

High temperature (HT) electronics applications will require the development of a broad range of devices made using different materials. Among these devices, high-electron mobility transistors (HEMTs) made with GaN and its alloys are attractive for high-power radio frequency (RF) applications. In this manuscript, we tested AlGaN/GaN HEMT devices having ~140-nm gate length at different temperatures up to 500 °C. Devices were fabricated using Air Force Research Laboratory’s (AFRL’s) 140-nm ${T}$ -gate process technology. The performance degradation measured in different devices was analyzed by considering changes in different device parameters and by using appropriate device physics. Cross-sectional materials characterization using scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) was performed to understand the origin of performance degradation. This understanding will allow us to design a sub- $\mu \text{m}$ GaN-based process technology compatible with HT RF applications.

Published
2024
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23. Accurate non-linear harmonic simulations at X-band using the ASM-HEMT model validated with NVNA measurements

Author

Miller, Nicholas C., primary, Davis, Devin T., additional, Khandelwal, Sourabh, additional, Sischka, Franz, additional, Gilbert, Ryan, additional, Elliott, Michael, additional, Fitch, Robert C., additional, Liddy, Kyle J., additional, Green, Andrew J., additional, Werner, Elizabeth, additional, Walker, Dennis E., additional, and Chabak, Kelson D., additional

Published
2022
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24. Accurate Nonlinear GaN HEMT Simulations from X- to Ka-Band using a Single ASM-HEMT Model

Author

Miller, Nicholas C., primary, Moser, Neil A., additional, Fitch, Robert C., additional, Gillespie, James K., additional, Liddy, Kyle J., additional, Walker, Dennis E., additional, Green, Andrew J., additional, Chabak, Kelson D., additional, Elliott, Michael, additional, Gilbert, Ryan, additional, Young, Richard, additional, Werner, Elizabeth, additional, Lindquist, Miles, additional, and Roblin, Patrick, additional

Published
2021
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25. RF Power Performance of Sc(Al,Ga)N/GaN HEMTs at Ka-Band

Author

Green, Andrew J., primary, Moser, Neil, additional, Miller, Nicholas C., additional, Liddy, Kyle J., additional, Lindquist, Miles, additional, Elliot, Michael, additional, Gillespie, James K., additional, Fitch, Robert C., additional, Gilbert, Ryan, additional, Walker, Dennis E., additional, Werner, Elizabeth, additional, Crespo, Antonio, additional, Beam, Edward, additional, Xie, Andy, additional, Lee, Cathy, additional, Cao, Yu, additional, and Chabak, Kelson D., additional

Published
2020
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26. Pulsed Power Performance of β-Ga₂O₃ MOSFETs at L-Band

Author

Moser, Neil A., primary, Asel, Tadj, additional, Liddy, Kyle J., additional, Lindquist, Miles, additional, Miller, Nicholas C., additional, Mou, Shin, additional, Neal, Adam, additional, Walker, Dennis E., additional, Tetlak, Steve, additional, Leedy, Kevin D., additional, Jessen, Gregg H., additional, Green, Andrew J., additional, and Chabak, Kelson D., additional

Published
2020
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27. Self-Heating Characterization of $\beta$ -Ga2O3 Thin-Channel MOSFETs by Pulsed ${I}$ –${V}$ and Raman Nanothermography

Author

Blumenschein, Nicholas A., primary, Moule, Taylor, additional, Dalcanale, Stefano, additional, Mercado, Elisha, additional, Singh, Manikant, additional, Pomeroy, James W., additional, Kuball, Martin, additional, Wagner, Gunter, additional, Paskova, Tania, additional, Muth, John F., additional, Chabak, Kelson D., additional, Moser, Neil A., additional, Jessen, Gregg H., additional, Heller, Eric R., additional, Miller, Nicholas C., additional, Green, Andrew J., additional, Popp, Andreas, additional, Crespo, Antonio, additional, Leedy, Kevin, additional, and Lindquist, Miles, additional

Published
2020
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31. Lateral β-Ga2O3 field effect transistors

Author

Chabak, Kelson D, primary, Leedy, Kevin D, additional, Green, Andrew J, additional, Mou, Shin, additional, Neal, Adam T, additional, Asel, Thaddeus, additional, Heller, Eric R, additional, Hendricks, Nolan S, additional, Liddy, Kyle, additional, Crespo, Antonio, additional, Miller, Nicholas C, additional, Lindquist, Miles T, additional, Moser, Neil A, additional, Fitch, Robert C, additional, Walker, Dennis E, additional, Dorsey, Donald L, additional, and Jessen, Gregg H, additional

Published
2019
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32. Self-Heating Characterization of β-Ga2O3 Thin-Channel MOSFETs by Pulsed I – V and Raman Nanothermography.

Author

Blumenschein, Nicholas A., Moule, Taylor, Dalcanale, Stefano, Mercado, Elisha, Singh, Manikant, Pomeroy, James W., Kuball, Martin, Wagner, Gunter, Paskova, Tania, Muth, John F., Chabak, Kelson D., Moser, Neil A., Jessen, Gregg H., Heller, Eric R., Miller, Nicholas C., Green, Andrew J., Popp, Andreas, Crespo, Antonio, Leedy, Kevin, and Lindquist, Miles

Subjects
THERMAL resistance, METAL oxide semiconductor field-effect transistors, LOGIC circuits, ELECTRIC potential measurement
Abstract

β-Ga2O3 thin-channel MOSFETs were evaluated using both dc and pulsed I – V measurements. The reported pulsed I – V technique was used to study self-heating effects in the MOSFET channel. The device was analyzed over a large temperature range of 23 °C–200 °C. A relationship between dissipated power and channel temperature was established, and it was found that the MOSFET channel was heating up to 208 °C when dissipating 2.5 W/mm of power. The thermal resistance of the channel was found to be 73 °C-mm/W. The results are supported with the experimental Raman nanothermography and thermal simulations and are in reasonable agreement with pulsed I – V findings. The high thermal resistance underpins the importance of optimizing thermal management in future Ga2O3 devices. [ABSTRACT FROM AUTHOR]

Published
2020
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45. Interactive modeling as a forcing function for research in the physiology of human performance.

Author

Miller, Nicholas C. and Walters, Richard F.

Abstract

Physiological models are frequently designed to study a single-organ system or to investigate the differ ences in response of alternative representations of the same system. In this study, an interactive model portrays the human circulatory, thermoregulatory, and energy-exchange systems as an intercoupled set and serves as a means of communication between mem bers of an interdisciplinary research team. The assumptions necessary to couple these systems are described, as are the research team's techniques for using the model. The goal is to develop the model to the point of accurately simulating the real-world behavior of the coupled systems in normal human beings and in those with certain diseases. The model serves to focus the team's attention on areas requiring additional experimentation, which in turn leads to modifications to improve the model. [ABSTRACT FROM PUBLISHER]

Published
1974
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46. Next Generation Pharmaceutical Impactor (A New Impactor for Pharmaceutical Inhaler Testing). Part I: Design

Author

Marple, Virgil A., Roberts, Daryl L., Romay, Francisco J., Miller, Nicholas C., Truman, Keith G., Van Oort, Michiel, Olsson, Bo, Holroyd, Michael J., Mitchell, Jolyon P., and Hochrainer, Dieter

Abstract

A new cascade impactor has been designed specifically for pharmaceutical inhaler testing. This impactor, called the Next Generation Pharmaceutical Impactor (NGI), has seven stages and is intended to operate at any inlet flow rate between 30 and 100 L/min. It spans a cut size (D50) range from 0.54-μm to 11.7-μm aerodynamic diameter at 30 L/min and 0.24 μm to 6.12 μm at 100 L/min. The aerodynamics of the impactor follow established scientific principles, giving confident particle size fractionation behavior over the design flow range. The NGI has several features to enhance its utility for inhaler testing. One such feature is that particles are deposited on collection cups that are held in a tray. This tray is removed from the impactor as a single unit, facilitating quick sample turn-around times if multiple trays are used. For accomplishing drug recovery, the user can add up to approximately 40 mL of an appropriate solvent directly to the cups. Another unique feature is a micro-orifice collector (MOC) that captures in a collection cup extremely small particles normally collected on the final filter in other impactors. The particles captured in the MOC cup can be analyzed in the same manner as the particles collected in the other impactor stage cups. The user-friendly features and the aerodynamic design principles together provide an impactor well suited to the needs of the inhaler testing community.

Published
2003
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47. Test method for evaluation of loss of prime in metered-dose aerosols

Author

Fiese, Eugene F., Gorman, William G., Dolinsky, Donna, Harwood, Richard J., Hunke, William A., Miller, Nicholas C., Mintzer, Harvey, and Harper, Nancy J.

Abstract

A new test method is described for assessing the loss of prime in metered-dose aerosols. Two representative metered-dose valve designs and two storage positions were used to assess the utility of this test method at three different sites. Loss of prime, defined as a valve delivery 15% below the mean, was detected in three of the four test configurations. The first significant loss of prime in this study was observed at the two-week time point for valves without drain tanks stored in the upright position. Onset of loss of prime was shown to be dependent on valve design as well as storage position, thus alternate valves or storage conditions should yield different results. This test method appeared to be reproducible over the three test sites, with a slight variation in results attributed to differences in storage conditions and agitation during sample handling. This test method intentionally excluded agitation which is in sharp contrast to the normal “shake well before use” instruction to the patient. Following one priming actuation, all of the valves returned to their mean valve delivery.

Published
1988
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50. Comparative Absorption of Atropine from a MeteredDose Inhaler and an Intramuscular Injection

Author

Kehe, Colin R., Lasseter, Kenneth C., Miller, Nicholas C., Wick, Karen A., Shamblen, E. Cooper, Ekholm, Bruce P., Sandahl, Jane H., Chang, Shaw F., Goldlust, M. Barry, Kvam, Donald C., and Harrison, Lester I.

Abstract

The inhalation of atropine sulfate from a pressurized metered-dose inhaler was investigated in a nonrandomized four-period rising-dose study. Eight healthy, nonsmoking subjects received 1.7, 3.4, and 5.2 mg of atropine sulfate by inhalation and 1.67 mg of atropine free base (equivalent to 2 mg of atropine sulfate) by intramuscular (i.m.) injection. Serum atropine sulfate concentrations were measured over a 24-h period by gas chromatography/mass spectrometry. Mean serum concentrations increased nonproportionally as the inhaled dose increased. Mean peak concentrations were 4.9, 6.1, and 7.9 ng/ml for the inhaled doses and 8.4 ng/ml for the i.m. dose. Typical anticholinergic effects were seen after all doses.

Published
1992

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