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Reduction of base access resistance in AlGaN/GaN heterojunction bipolar transistors using GaInN base cap layer and selective epitaxial growth

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2005 Materials Research Society Fall Meeting

作者： Shah, Jay M. Gessmann, Thomas Luo, Hong Xi, Yangang Chen, Kaixuan Kim, Jong Kyu Fred Schubert, E. Electrical Computer and Systems Engineering Department Rensselaer Polytechnic Institute Troy NY 12180-3590 United States Department of Physics Applied Physics and Astronomy Rensselaer Polytechnic Institute Troy NY 12180-3590 United States

ISBN: (纸本)1558998462

One of the major challenges affecting the performance of Npn AlGaN/GaN heterojunction bipolar transistors (HBTs) is the high base access resistance, which is comprised of the base contact resistance and the base bulk resistance. A novel concept is proposed to reduce the base access resistance in Npn AlGaN/GaN HBTs by employing polarization-enhanced contacts and selective epitaxial growth of the base and emitter. In addition, this technique reduces the exposed base surface area, which results in a lower surface recombination current. Such a structure would enable better performance of AlGaN/GaN HBTs in terms of higher current gain and a lower offset voltage. Theoretical calculations on polarization-enhanced contacts predict p-type specific contact resistance lower than 10-55 Ωcm2. Experimental-results using transmission line measurement (TLM) technique yield specific contact resistances of 5.6×10-4 Ωcm2 for polarization-enhanced p-type contacts and 7.8×10-2 Ωcm2 for conventional p-type contacts. © 2006 Materials Research Society.

关键词： Heterojunction bipolar transistors

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Integrated semiconductor optical sensors for chronic, minimally-invasive imaging of brain function

Integrated semiconductor optical sensors for chronic, minima...

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28th Annual International Conference of the IEEE engineering in Medicine and Biology Society, EMBS'06

作者： Lee, Thomas T. Levi, Ofer Jianhua, Cang Kaneko, Megumi Stryker, Michael P. Smith, Stephen J. Shenoy, Krishna V. Harris Jr., James S. IEEE Department of Electrical Engineering Stanford University Stanford CA 94303 United States Departments of Electrical Engineering and Applied Physics Stanford University Stanford CA 94305 United States Department of Physiology University of California San Francisco 94143 United States Department of Molecular and Cellular Physiology Neurosciences Program Stanford University Stanford CA 94305 United States Department of Electrical Engineering Neurosciences Program Stanford University Stanford CA 94305 United States Departments of Electrical Engineering Applied Physics and Materials Science and Engineering Stanford University Stanford CA 94305 United States

ISBN: (纸本)1424400325

Intrinsic Optical Signal (IOS) imaging is a widely accepted technique for imaging brain activity. We propose an integrated device consisting of interleaved arrays of gallium arsenide (GaAs) based semiconductor light sources and detectors operating at telecommunications wavelengths in the near-infrared. Such a device will allow for long-term, minimally invasive monitoring of neural activity in freely behaving subjects, and will enable the use of structured illumination patterns to improve system performance. In this work we describe the proposed system and show that near-infrared IOS imaging at wavelengths compatible with semiconductor devices can produce physiologically significant images in mice, even through skull. © 2006 IEEE.

关键词： Optical sensors

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A compact single-walled carbon nanotube transistor integrated with a silicon MOSFET using a single common gate

A compact single-walled carbon nanotube transistor integrate...

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2006 MRS Fall Meeting

作者： Lin, Hao Park, Yong Wook Tiwari, Sandip Department of Applied and Engineering Physics Cornell University Ithaca NY 14850 United States Namseoul University Chonan-si Korea Republic of Department of Electrical and Computer Engineering Cornell University Ithaca NY 14850 United States

ISBN: (纸本)9781604234152

Single-walled carbon nanotubes have been integrated on top of an individual CMOS device using lithography, chemical vapor deposition and chemical mechanical planarization. Hybrid integration of silicon and nanotube transistors is demonstrated for the first time by making an inverter with a p-type CNTFET placed on top of an n-type MOSFET. A polysilicon gate is positioned between the silicon device channel and carbon nanotube for dense integration of opposite-polarity devices. Such a configuration offers many advantages for high-density electronics and ultra-sensitive detection. © 2007 Materials Research Society.

关键词： MOSFET devices

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Cooperative defence against DDoS attacks

Cooperative defence against DDoS attacks

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作者： Zhang, Guangsen Parashar, Manish 628 CoRE Department of Electrical and Computer Engineering Rutgers the State University of New Jersey 94 Brett Road Piscataway NJ 08854-8058 Department of Electrical and Computer Engineering Rutgers University Rutgers University Applied Software Systems Laboratory IEEE Computer Society Distinguished Visitor Program ACM

Distributed denial of service (DDoS) attacks on the Internet have become an immediate problem. As DDoS streams do not have common characteristics, currently available intrusion detection systems (IDS) cannot detect them accurately. As a result, defend DDoS attacks based on current available IDS will dramatically affect legitimate traffic. In this paper, we propose a distributed approach to defend against distributed denial of service attacks by coordinating across the Internet. Unlike traditional IDS, we detect and stop DDoS attacks within the intermediate network. In the proposed approach, DDoS defence systems are deployed in the network to detect DDoS attacks independently. A gossip based communication mechanism is used to exchange information about network attacks between these independent detection nodes to aggregate information about the overall network attacks observed. Using the aggregated information, the individual defence nodes have approximate information about global network attacks and can stop them more effectively and accurately. To provide reliable, rapid and widespread dissemination of attack information, the system is built as a peer to peer overlay network on top of the internet. Copyright © 2006, Australian computer Society Inc.

关键词： Security systems

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Plan switching: An approach to plan execution in changing environments 20

Plan switching: An approach to plan execution in changing en...

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20th IEEE International Parallel and Distributed Processing Symposium, IPDPS 2006

作者： Yu, Han Malinescu, Dan C. Wu, Annie S. Siegel, Howard Jay Daley, Rose A. Wang, I.-Jeng School of Electrical Engineering and Computer Science University of Central Florida Orlando FL 32816 United States Department of Electrical and Computer Engineering Colorado State University Fort Collins CO 80523-1373 United States Johns Hopkins University Applied Physics Laboratory 11100 Johns Hopkins Road Laurel MD 20723-6099 United States

ISBN: (纸本)1424400546

The execution of a complex task in any environment requires planning. Planning is the process of constructing an activity graph given by the current state of the system, a goal state, and a set of activities. If we wish to execute a complex computing task in a heterogeneous computing environment with autonomous resource providers, we should be able to adapt to changes in the environment. A possible solution is to construct a family of activity graphs beforehand and investigate the means of switching from one member of the family to another when the execution of one activity graph fails. In this paper, we study the conditions when plan switching is feasible. Then we introduce an approach for plan switching and report the simulation results of this approach. © 2006 IEEE.

关键词： Distributed computer systems

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Internal omni-directional reflector using a low refractive index material for light-emitting diodes

Internal omni-directional reflector using a low refractive i...

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Conference on Lasers and Electro-Optics, CLEO 2006

作者： Xi, J.-Q. Ojha, Manas Cho, Woojin Wetzel, Christian Gessmann, T. Schubert, E.F. Plawsky, J.L. Gill, W.N. The Future Chips Constellation United States Department of Physics Applied Physics and Astronomy Rensselaer Polytechnic Institute Troy NY 12180 United States Department of Chemical and Biological Engineering Rensselaer Polytechnic Institute Troy NY 12180 United States Department of Electrical Computer and Systems Engineering Rensselaer Polytechnic Institute Troy NY 12180 United States

ISBN: (纸本)1557528136

A triple-layer omni-directional reflector (ODR), which consists of a semiconductor, a transparent quarter-wavelength dielectric layer, and a metal layer, has high reflectivity at all angles of incidence when used as an internal ODR. In this paper, triple-layer ODRs are demonstrated that incorporate nanoporous SiO2, a new low-refractive-index (low-n) material with refractive index « 1.46. Internal reflectivity measurements, including the angular dependence of R, are presented. The angle-integrated TE/TM-averaged reflectivity of the triple-layer reflector using nanoporous SiO2 is 99.4 %. This is the highest ever reported averaged reflectivity for an internal ODR. The mirror loss of the triple-layer ODR is a factor of 7 lower than the mirror loss of conventional metal reflectors. The results indicate the great potential of the ODR for light-emitting diodes with high light-extraction efficiency. © 2005 OSA/CLEO 2005.

关键词： Silica

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A brokering framework for large-scale heterogeneous systems 20

A brokering framework for large-scale heterogeneous systems

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20th IEEE International Parallel and Distributed Processing Symposium, IPDPS 2006

作者： Bai, Xin Bölöni, Ladislau Malinescu, Dan C. Siegel, Howard Jay Daley, Rose A. Wang, I.-Jeng University of Central Florida School of Electrical Engineering and Computer Science Orlando FL 32816-2362 United States Colorado State University Department of Electrical and Computer Engineering Fort Collins CO 80523-1373 United States Johns Hopkins University Applied Physics Laboratory 11100 Johns Hopkins Road Laurel MD 20723-6099 United States

ISBN: (纸本)1424400546

In this paper we discuss the role of a broker in a market-oriented resource allocation model for large-scale heterogeneous systems. The simplified model is based upon a three party system, provider-broker-consumer. The allocation of resources is determined by their price, their utility to the consumer, and by the satisfaction of the consumer. The role of the broker is to add societal objectives to resource allocation algorithms and to mediate between greedy consumers and selfish providers. A simulation experiment was conducted to study the transient and the steady-state behavior of several performance measures, including the average consumer satisfaction, the average utility, and the hourly revenue. © 2006 IEEE.

关键词： Distributed computer systems

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Total dose radiation response of nitrided and non-nitrided SiO 2/4H-SiC MOS capacitors

Total dose radiation response of nitrided and non-nitrided S...

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作者： Dixit, Sriram K. Dhar, Sarit Rozen, John Wang, Sanwu Schrimpf, Ronald D. Fleetwood, Daniel M. Pantelides, Sokrates T. Williams, John R. Feldman, Leonard C. IEEE Interdisciplinary Materials Science Program Vanderbilt University Nashville TN 37235 United States Department of Physics and Astronomy Vanderbilt University Nashville TN 37235 United States Department of Physics and Engineering Physics University of Tulsa Tulsa OK 74104 United States Department of Electrical Engineering and Computer Science Vanderbilt University Nashville TN 37235 United States Physics Department Auburn University Auburn AL 36849 United States

The total dose radiation response of nitrided and nonnitrided n-type 4H-SiC is reported for metal oxide semiconductor capacitors exposed to 10-keV X-rays under positive bias. The radiation response is affected strongly by differences in the SiC band gap and interface/near interface SiO2 trap density from typical Si MOS devices. Significantly higher net trapped positive charge densities were observed in nitrided n-SiC MOS capacitors compared to the non-nitrided samples. The mechanisms contributing to the differences in the charge trapping in these devices are discussed. Differences in the interfacial layer between SiO2/Si and SiO2/SiC are responsible for the observed dissimilarities in charge trapping behavior. © 2006 IEEE.

关键词： MOS capacitors

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Beam Injection and Matching Studies at the University of Maryland Electron Ring (UMER)

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AIP Conference Proceedings 2006年第1期877卷 687-693页

作者： Jayakar C. T. Thangaraj R. A. Kishek S. Bernal M. Reiser D. Stratakis M. Walter B. Quinn D. Sutter B. Beaudoin C. Papadopoulous G. Bai C. Wu P. G. O’Shea §Institute of Research in Electronics and Applied Physics University of Maryland College Park Maryland *Department of Electrical and Computer Engineering University of Maryland College Park Maryland

The University of Maryland Electron Ring (UMER) is a scaled model to investigate the physics of such intense beams. It uses a 10‐keV electron beam along with other scaled beam parameters that model the larger machines but at a lower cost. Recently, multi turn operation of the ring (3.6 m diameter) has been achieved. In order to have full current transport of the electron beam, and to increase the number of turns of the beam around the ring, injection of the beam from the straight section into the ring becomes crucial. In this work, we report experimental results from the injection and matching of a space charge dominated beam and an emittance dominated beam. We also describe and analyze two methods of injection of the electron beam from the straight section into the ring. In one of the methods, the two injection quads are fixed to a preset value, while in the other both the injection quads are switched off (Collins injection).

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Nanoparticle-loaded encapsulation materials for light-emitting diode applications

Nanoparticle-loaded encapsulation materials for light-emitti...

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2006 MRS Fall Meeting

作者： Mont, F.W. Luo, H. Schubert, M.F. Kim, J.K. Schubert, E.F. Siegel, R.W. Future Chips Constellation Department of Electrical Computer and Systems Engineering Rensselaer Polytechnic Institute Troy NY 12180 United States Future Chips Constellation Department of Physics Applied Physics and Astronomy Rensselaer Polytechnic Institute Troy NY 12180 United States Department of Materials Science and Engineering Rensselaer Nanotechnology Center Rensselaer Polytechnic Institute Troy NY 12180 United States

ISBN: (纸本)9781604234114

Nanoparticle-loaded encapsulants provide unique optical and material properties for the enhancement of light-extraction efficiency in light-emitting diodes (LEDs). We report on the uniform dispersion of TiO2 nanoparticles with average diameter of 40 nm in epoxy, and the demonstration of a refractive index (n) of 1.68 at 400 nm wavelength, higher than that of pure epoxy (n = 1.53). It is found that proper chemical surfactants and nanoparticle preparation are critical to eliminate agglomeration of nanoparticles. Theoretical analysis of optical scattering in nanoparticle-loaded encapsulation materials reveals that although the size and loading factor of nanoparticles greatly influence scattering, specular transparency of the encapsulant film occurs if the thicknesses of the films are kept below the optical scattering length. Furthermore, the encapsulants benefit from an optimized scattering coefficient as demonstrated by three-dimensional ray-tracing simulations showing light-extraction efficiency enhancements greater than 50%. © 2007 Materials Research Society.

关键词： Nanoparticles

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