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Electron Devices, IEEE Transactions on

Issue 12 • Date Dec 1990

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Displaying Results 1 - 25 of 34
  • High-power microwave generation using optically activated semiconductor switches

    Publication Year: 1990 , Page(s): 2439 - 2448
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (832 KB)  

    The two prominent types of optically controlled switches, the optically controlled linear (OCL) switch and the optically initiated avalanche (OIA) switch, are described, and their operating parameters are characterized. Two transmission line approaches, one using a frozen-wave generator and the other using an injected-wave generator, for generation of multiple cycles of high-power microwave energy using optically controlled switches are discussed. The point design performances of the series-switch, frozen-wave generator and the parallel-switch, injected-wave generator are compared. The operating and performance limitations of the optically controlled switch types are discussed, and additional research needed to advance the development of the optically controlled, bulk, semiconductor switches is indicated View full abstract»

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  • Scandium supply after ion bombardment on scandate cathodes

    Publication Year: 1990 , Page(s): 2589 - 2594
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (628 KB)  

    A scandium, barium, and oxygen coverage of monolayer order is essential to the high-emission capability of scandate cathodes. The relationship between surface coverage and emission is demonstrated by combined scanning Auger and emission measurements. A problem with the known cathodes is that the emission recovery after ion bombardment, as may occur during CRT processing, is not yet complete. The problem cannot be solved by simply constructing a mixed-matrix cathode of W and Sc grains because of huge evaporation of Sc during sintering and oxidation of the remainder during subsequent impregnation. How the scandium can be effectively surrounded by a protective layer resulting in considerably improved scandium supply, is discussed. Moreover, experimental results indicate the possibility for further simplification of the cathode manufacture. The latter is shown with the aid of cathodes containing compounds which exhibit Sc surface segregation on heating View full abstract»

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  • Electrooptic imaging of surface electric fields in high-power photoconductive switches

    Publication Year: 1990 , Page(s): 2449 - 2458
    Cited by:  Papers (8)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (928 KB)  

    A two-dimensional electrooptic probe was used to image the electric field in high-power photoconductive switches during switch operation. A LiTaO3 crystal, covering the entire active area of the photoconductive switch, coupled the surface electric field with the polarization of an optical probe pulse. The optical probe was imaged onto a two-dimensional detector array, producing snapshots of the surface field with 200-ps time resolution and 3-μm spatial resolution. The probe system was used to monitor the electric field in the electrode gap of high-voltage switches, the focus of investigation being the collapse of the electric field in a GaAs bulk switch as it was switched with a λ=1.06 μm optical pulse. The switching speed and generation of field enhancements were found to be dependent on the illumination configuration and the applied electric field, which varied from 0 to 15 kV/cm. Switching efficiency was found to decrease with increasing field View full abstract»

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  • Photoconductive switches for AC circuit protection

    Publication Year: 1990 , Page(s): 2526 - 2531
    Cited by:  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB)  

    The basic suitability of the photoconductive circuit element (PCE) for protective switching applications in AC power transmission and distribution circuits is examined. Specific applications include circuit breakers and fault-current limiters. This work considers a hybrid switching mechanism, which consists of a parallel arrangement of the PCE with a low-capacity mechanical switch. Electrical, optical, and thermal models are developed for the PCE device, which are incorporated in a system-level computer simulation of a power test circuit. Simulation results show the feasibility of the hybrid switching concept, although device sizes appear to be relatively large due to thermal dissipation requirements View full abstract»

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  • Optical control of semiconductor closing and opening switches

    Publication Year: 1990 , Page(s): 2426 - 2438
    Cited by:  Papers (22)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1148 KB)  

    Recent progress in the research of high-power photoconductive semiconductor switches is reviewed. Material issues and switch design considerations are discussed. High-power ultra-wide-band microwave generation using these switches and a pulse-forming network is presented. The application of the photoconductive switch both as a closing and and as an opening switch in an inductive energy storage system has been demonstrated. Electric pulse compression with a peak power gain of 30 has been observed. Future prospects in this area of research are discussed View full abstract»

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  • Investigation of Sc2O3 behavior in Sc2 O3-dispersed oxide cathodes

    Publication Year: 1990 , Page(s): 2605 - 2611
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (732 KB)  

    Sc2O3 behavior in oxide cathodes is investigated through the analyses of AES, XPS, and EPMA. It has been shown that Sc2O3 plays a significant role in maintaining higher surface concentration of Ba atoms. Thermochemical considerations have indicated possible reactions of Sc2O3 with interface compounds. It is concluded that Sc2O3 decomposes interface compounds and generates more Ba atoms in the vicinity of a base metal, and Sc2 O3 inside of an electron emissive layer also has an effect on reducing surface Ba evaporation and maintaining higher electric conductivity View full abstract»

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  • Effective work function measurements of advanced cathode materials via a thermionic projection microscope system

    Publication Year: 1990 , Page(s): 2568 - 2574
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (760 KB)  

    An experimental method for simultaneously determining the effective thermionic work functions of major planes of single-crystal surfaces is reported. This method has been used to examine transition metal carbides and the emitting surface of a prototype, thermionic fuel element (TFE) cathode. In addition to generating work function values, this method maps variations in the distribution of work functions. Applications for transition metal carbides could include cathodes for advanced thermionic energy conversion, radiation immune microcircuitry, β-SiC substrates, or high current density field emission cathodes. Transition metal carbide single-crystal specimens were prepared by arc floating zone refinement from sintered stock. Hemispherical cathodes, 0.75 mm in diameter, were made from these carbides and from a machined sample of a high creep strength, emitter prototype. Work function ordering for various crystal planes is reported through the thermionic projection microscope image-processing method. To understand the work function values obtained, scanning electron microscopy and optical microscopy were utilized. An optical image of a cross section of the fuel element which was electrochemically etched to reveal the crystalline structure and orientation of the CVD-W layer is presented View full abstract»

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  • A high-efficiency ferruleless coupled-cavity traveling-wave tube with phase-adjusted taper

    Publication Year: 1990 , Page(s): 2638 - 2643
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (444 KB)  

    The design and performance of the first traveling-wave tube (TWT) to be built with a phase-adjusted taper (PAT) is discussed. By adjusting the phase of the electron bunch with respect to the RF wave for strong electron bunch formation at the beginning of the taper and strong power conversion at the end, the PAT achieves a high efficiency of power conversion from the electron beam to the RF wave. A PAT incorporated into the output section of a baseline 29-30 GHz ferruleless coupled-cavity TWT experimentally increased the peak RF power from 420 to 1000 W and the peak RF interaction efficiency from 9.6 to 22.6% View full abstract»

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  • Life test studies on MM-cathodes

    Publication Year: 1990 , Page(s): 2558 - 2563
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    Mixed metal matrix cathodes (MM-cathodes) were optimized and their life behavior was tested in different test vehicles. In two separate life test programs, 57 MM-cathodes with a W/Os matrix were investigated in test vehicle (tetrodes) where the cathode environment was similar to that of a tube. In parallel, a further 100 MM-cathodes in other types of test vehicles were operated for supplementary investigations and cathode design optimization. The operational temperatures were between 880°C B and 1200°CB (brightness). One group of cathodes was operated at constant anode voltage with an initial current density of 0.75 A/cm2, and the other group was operated with a loading of 2 A/cm2 for as long as the anode voltage could be adjusted. The cathodes at lower temperatures (⩽1100°CB ) have accumulated more than 40000 h of operation. The results are used to establish cathode life prediction models as a function of temperature and current density. The excellent capability of the cathode type for long-life space applications has been demonstrated View full abstract»

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  • The recovery behavior of semi-insulating GaAs in electron-beam-controlled switches

    Publication Year: 1990 , Page(s): 2478 - 2485
    Cited by:  Papers (17)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (716 KB)  

    Semi-insulating GaAs is experimentally studied with respect to its application in electron-beam-controlled switches. The dark current through the switch is measured both before and after electron-beam irradiation. A lock-on effect, similar to that seen in photoconductive switches, is observed after the electron beam is terminated. This effect is characterized by the switch current continuing to flow, locked to a certain voltage, as long as the voltage is applied across the switch. A possible explanation for this effect, based on the process of electron and hole injection at the contacts, is presented. A method to minimize double injection is offered to make the electron-beam-controlled switch, along with the photoconductive switch, practical for use as both an opening and closing switch View full abstract»

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  • Photoconductive nanosecond pulse generation utilizing radial transmission lines

    Publication Year: 1990 , Page(s): 2506 - 2510
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (412 KB)  

    A nanosecond, kilovolt pulse generator utilizing a radial transmission line was investigated. The device incorporates a gallium arsenide, photoconductive switch to connect the radial line to the coaxial output. Identical gridded electrodes are used on opposite sides of the switch. Switching is achieved with a 75-ps-wide pulse from a mode-locked Nd:YAG laser. In addition to the radial design, a quasi-radial structure was also investigated, in which improvements in rise time and pulsewidth were achieved at the expense of voltage gain. For the same charging voltage of 9.2 kV, the radial device delivered a 10-kV, 1.3-ns-wide pulse, while the quasi-radial device gave a 6-kV, 500-ps-wide pulse. An integrated pulser design in which the switch and the dielectric medium between conducting planes are combined into a single semi-insulating GaAs wafer is described. The potential advantages of such a device are discussed View full abstract»

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  • Free electron laser in a stripline geometry

    Publication Year: 1990 , Page(s): 2614 - 2618
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (372 KB)  

    A thin dielectric slab over a conducting sheet is presented as a low-loss slow-wave guiding system. When one introduces a magnetic wiggler into the system one may efficiently excite millimeter waves by passing a sheet electron beam just above the dielectric surface. For realistic parameters, the energy requirements on the beam are greatly reduced due to the wiggler. The frequency ω1 and the growth rate G are very sensitive to beam energy. G scales as Ib1/3B2/3 with beam current Ib and wiggler strength B 0, and decreases with increasing width of the dielectric and increasing ω1 View full abstract»

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  • High-voltage picosecond photoconductor switch based on low-temperature-grown GaAs

    Publication Year: 1990 , Page(s): 2493 - 2498
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (516 KB)  

    A GaAs material grown by molecular beam epitaxy at a low substrate temperature was used to fabricate a photoconductor switch that produces 6-V picosecond electrical pulses. The pulses were produced on a microwave coplanar-strip transmission line lithographically patterned on the low-temperature (LT) GaAs. A 150-fs laser pulse was used to generate carriers in the LT GaAs gap between the metal strips, partially shorting a high DC voltage placed across the lines. The 6-V magnitude of the electrical pulses obtained is believed to be limited by the laser pulse power and not by the properties of the LT GaAs. Experiments were also performed on a picosecond photoconductor switch fabricated on a conventional ion-damaged silicon-on-sapphire substrate. Although comparable pulse durations were obtained, the highest pulse voltage achieved with the latter device was 0.6 V View full abstract»

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  • Outgassing of CRT shadow mask coatings caused by electron bombardment

    Publication Year: 1990 , Page(s): 2644 - 2651
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (716 KB)  

    A UHV system with a quadrupole mass spectrometer in a nude condition was used to investigate the outgassing characteristics of the coatings of CRT shadow mask during electron bombardment. The coatings of Bi2O3, WO3 and Fe3O4 were electron bombarded with energies from 15 to 30 keV and currents up to 100 μA. The Bi2O3 coating released a larger amount of gas than WO3 and Fe3O 4, but its amount decreased to the same extent as that of the others with heat treatment at temperatures higher than 450°C. The main components of released gas were CO, CO2, CH4, and H2, and the release of O2 was also observed for the Bi2O3 coating without heat treatment. This O2 release was found to be caused by the decomposition of unstable carbonate, which was formed by the reaction of Bi2O 3 with CO2 in the presence of moisture during the preparation of the coating. These outgassing behaviors are discussed quantitatively from the viewpoint of preventing oxidizing gas release View full abstract»

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  • Photoconductive switching using polycrystalline ZnSe

    Publication Year: 1990 , Page(s): 2517 - 2519
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (176 KB)  

    Photoconductive switching was investigated using polycrystalline ZnSe illuminated by a Coumarine 480 dye laser pumped by an excimer laser. An intracavity grating was used to tune the dye laser wavelength to maximize the output voltage. High mobility (>900 cm2/V-s), a carrier lifetime under 1 ns, and operation at DC bias fields of 45 kV/cm were observed View full abstract»

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  • Calculation of TM0n mode dispersion relations in rippled-wall waveguides

    Publication Year: 1990 , Page(s): 2619 - 2621
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB)  

    A novel technique for calculating the dispersion relation for TM 0n modes in a rippled-wall waveguide is reported. A standard eigenvalue solver for the two-dimensional Helmholtz equation is used to calculate the frequencies for several special values of the wavenumber. For other wavenumbers, the frequencies of the lowest order mode are calculated by interpolation using a function based on an equivalent circuit model, whose parameters are determined from the numerically calculable cases. The advantages of this approach are ease of use and the ability to handle a variable dielectric constant inside of the waveguide View full abstract»

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  • The extended Schottky cathode

    Publication Year: 1990 , Page(s): 2575 - 2580
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (464 KB)  

    Cathodes operating in the range of electric field strength and temperatures falling within the extended Schottky domain are discussed for applications requiring high current densities from a broad area cathode. Generally, these cathodes are operated in a pulsed high-voltage mode. Current densities of up to 300 A/cm2 have been achieved without breakdown. Cathode performance is limited by space-charge effects and excessive evaporation at the high operating temperatures required View full abstract»

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  • New findings of pulsed surface breakdown along silicon in vacuum

    Publication Year: 1990 , Page(s): 2466 - 2471
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (664 KB)  

    Leakage and partial-breakdown characteristics of high-purity (ρ>30 kΩ-cm) bulk silicon in vacuum (~10-6 torr) under impulse voltage stress (0.39/10 μs) are discussed. The discussion is focused on the mechanism associated with the partial-breakdown phase. The mechanism is believed to be due mainly to injection followed by avalanche breakdown, from many local spots at the cathode contact. Thermal and field emission processes are also proposed, along with the avalanche process, to describe the partial breakdown phase of silicon. These experimental findings clearly show that the injection process is a process through the bulk rather than along the surface of a specimen. More importantly, the final surface flashover is believed to be initiated by the bulk injection mechanism View full abstract»

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  • RADC cathode life test program

    Publication Year: 1990 , Page(s): 2612 - 2613
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (120 KB)  

    This brief is an update of the RADC cathode life test program and includes details of evaluation procedures, progress, and future plans. A technique has been developed which permits repeatable temperature measurements on cathode test vehicles using a two-color pyrometer. The setup of the pyrometer for the cathode activity plot measurements is critical. The technique developed, when compared to the previously used measurement procedures, has several advantages: (1) an increase in the repeatability of the measurement data; (2) decreased instrumentation setup time; (3) adjustments eliminating any jarring or jolting of the instrumentation during setup positioning; and (4) different individuals can perform the measurements and obtain similar results View full abstract»

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  • Ir-coated dispenser cathode for CRT

    Publication Year: 1990 , Page(s): 2564 - 2567
    Cited by:  Papers (2)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB)  

    A compact dispenser cathode has been developed for application to cathode ray tubes (CRTs). A cathode emitter, comprising BaO, CaO, and Al 2O3 in a molar ratio of 4:1:1, was impregnated into a porous tungsten pellet. An intermetallic compound of tungsten and iridium was formed on the cathode pellet. Heater ratings were 6.3 V×0.2 A. Emission characteristics were measured by using color CRTs. As a result, a cathode peak loading of 15 A/cm2 was ensured in the space-charge region. Furthermore, life tests with a peak loading of 7.5 A/cm2 were conducted over 10000 h. The decrease in emission current after 10000 h was within only 10% of the initial value. Reliability of cathode performance was assured in terms of breakdown potential between the heater and the cathode, emission characteristics, life performance, grid emission, and the drift in cutoff potential. In addition, the effects of the coating thickness on the emission characteristics are discussed View full abstract»

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  • Photoconductive semiconductor switch experiments for pulsed power applications

    Publication Year: 1990 , Page(s): 2472 - 2477
    Cited by:  Papers (30)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB)  

    Experiments have been performed to develop photoconductive semiconductor switches (PCSSs) for pulsed power applications that cannot be implemented with traditional high-power switching technology. A scalable lateral PCSS configuration has been tested and has demonstrated a potential for faster risetimes, less jitter, lower inductance, faster recovery, and optical triggering for new pulse power projects. These switches have been used as both closing and toggling switches at repetition rates up to 40 MHz. A high-field, gain mechanism (lock-on) was explored and tested which may eliminate the major disadvantage of this type of switch, its requirement for large optical trigger energies View full abstract»

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  • 35-kV GaAs subnanosecond photoconductive switches

    Publication Year: 1990 , Page(s): 2486 - 2492
    Cited by:  Papers (26)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (632 KB)  

    High-voltage, fast-pulse generation using GaAs photoconductive switches is investigated. It is possible to generate 35-kV pulses with risetimes as short as 135 ps using 5-mm gap switches, and electric field hold-off of greater than 100 kV/cm is achieved. An approximately 500-ps FWHM on/off electrical pulse is generated with an amplitude of approximately 3 kV using neutron-irradiated GaAs having short carrier lifetimes. Experimental results are described, and fabrication of switches and the diagnostics used to measure these fast signals are discussed. Experience with the nonlinear lock-on and avalanche modes of operation observed in GaAs is also described View full abstract»

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  • Photoconductive switching in diamond under high bias field

    Publication Year: 1990 , Page(s): 2511 - 2516
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    The limits of high-power, high-repetition-rate operation of photoconductive switches utilizing diamond are explored. To evaluate diamond as a photoconductor for high-power switching applications, the following experiments were performed: (1) measurement of switch resistance as a function of the bias electric field; (2) measurement of switch resistance as a function of laser intensity; (3) measurement of dependence of photoconductive response on the polarity of illuminated contact; and (4) evaluation of high repetition rate switching by using multiple laser pulse excitation View full abstract»

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  • Cathode performance in background of residual gases

    Publication Year: 1990 , Page(s): 2581 - 2584
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    It is shown to what extent residual gases appearing in microwave tubes affect the characteristics of the cathode, before and during operations. Tests were carried out on cathodes of the metal capillary type. The reaction takes place on the emitting surface of the cathodes, so the information retrieved can be applied to other types of cathode. Tungsten and osmium-coated tungsten cathodes were tested. The gases investigated were the following: helium, argon, nitrogen, carbon monoxide, carbon dioxide, oxygen, and methane View full abstract»

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  • Surface studies on scandate cathodes and synthesized scandates

    Publication Year: 1990 , Page(s): 2595 - 2604
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (776 KB)  

    Auger, ESCA, electron emission, evaporation, and desorption measurements were made on three different types of scandate surfaces. They are: (a) an impregnated top layer scandate cathode, (b) an unimpregnated top layer scandate cathode with a deposited barium or barium oxide adsorbate surface layer, and (c) a synthesized scandate surface, which replicates a scandate cathode surface. The purpose of these experiments was to determine the role that scandium oxide (Sc2O3) plays in making the scandate cathode a more copious electron emitter than the conventional impregnated-type cathode. The synthesized scandate surface experiments consisted of depositing multilayer scandium on a tungsten surface, oxidizing the scandium, and then depositing either Ba or BaO on the scandium oxide surface. The results of these measurements showed that the low work function portions of the thin-film scandate cathode are where the Sc2O3 is the substrate and BaO is the adsorbate View full abstract»

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IEEE Transactions on Electron Devices publishes original and significant contributions relating to the theory, modeling, design, performance and reliability of electron and ion integrated circuit devices and interconnects.

 

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Meet Our Editors

Acting Editor-in-Chief

Dr. Paul K.-L. Yu

Dept. ECE
University of California San Diego