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Nuclear Science, IEEE Transactions on

Issue 5 • Date Oct. 1965

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Displaying Results 1 - 24 of 24
  • [Front cover]

    Page(s): c1
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  • IEEE Nuclear Science Group

    Page(s): c2
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  • Table of contents

    Page(s): i
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  • The Nucleus

    Page(s): ii
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  • Seen at the Conference

    Page(s): ii - iii
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  • IEEE/GNS Radiation Effects Committee

    Page(s): iv
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  • 1965 Conference Committee

    Page(s): iv
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  • Guest Editorial

    Page(s): v
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  • The Space Radiation Environment

    Page(s): 1 - 17
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    The particle space radiation environment is reviewed and some of the latest models for the various phenomena are presented. The properties of the solar wind and interplanetary magnetic fields based on recent satellite measurements are given and solar proton events are discussed. The magnetospheric cavity and the character of the boundary between it and the solar wind based on Imp 1 results are shown. Flux maps and energy spectra for the inner and outer radiation zones are given and examples of temporal variations are shown. View full abstract»

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  • Simplified Techniques for Predicting Tree Responses

    Page(s): 30 - 39
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    Previous prediction methods1 are extended by analysis of new experimental data. Improved engineering techniques are developed for predicting equilibrium primary photocurrents from transistor electrical parameters. For silicon low power planar and mesa transistors, ¿ICBO is related to high base current electrical storage time by a simple prediction equation. A radiation storage time parameter is defined and theoretical and empirical equations for radiation storage time are developed. A radiation storage time transistor model and nomograph are presented to simplify pulsed radiation response predictions by circuit designers. The techniques are unique in predicting radiation responses entirely from measured preirradiation transistor electrical parameters. View full abstract»

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  • Methods for Measuring and Characterizing Transistor and Diode Large Signal Parameters for Use in Automatic Circuit Analysis Programs

    Page(s): 40 - 54
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    The mathematical bases of the Ebers-Moll, Charge-Control and Linvill models are discussed in order to establish the parameter requirements and the accuracy of these models. A recovery technique for measuring those parameters associated with minority carrier storage in devices is described and typical values are given for several high frequency devices. Other parameters, such as current gain and junction depletion capacitance, do not require special measurement procedures and in these cases the characterization of the bias dependence of the parameter is given primary emphasis. The use of the recovery technique in characterizing permanent radiation (neutron) damage and in studying damage mechanisms in transistors is also discussed. View full abstract»

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  • Generalized Model Analysis of Ionizing Radiation Effects in Semiconductor Devices

    Page(s): 55 - 68
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    The necessity of analyzing complex semiconductor device behavior in the radiation environment requires improved analytical methods for accurate representation. The purpose of this discussion is to present work done on the applicability of the Linvill lumped model in a generalized model analysis. The advantages of the lumped model technique include flexibility in detail of device representation (i.e., accuracy), an intimate coupling to the well known radiation effects in bulk semiconductor material, and a unified analytical technique for a wide range of devices. It is shown that the lumped model analysis provides an effective technique for analyzing simple as well as complex devices in a pulsed ionizing radiation environment. Included is the representation of a simple p-n junction diode, a grown-junction transistor; and a planar-diffused transistor with its monolithic-chip substrate and isolation junction. The lumped-model behavior of the diode and grown junction transistor is compared to previously available analytical results. Using measured parameter values, the quantitative lumped-model predictions are compared to experimentally observed transient radiation response. The transistor response is investigated as a function of quiescent emitter current and external base resistance. The effect of the substrate junction in the monolithic-chip transistor is qualitatively presented as a function of the transistor parameters and the substrate proximity. View full abstract»

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  • High-Energy Radiation Damage in Silicon Transistors

    Page(s): 69 - 77
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    An experimental investigation of electron and gamma ray damage in silicon transistors is presented. At low values of fluence (¿e < 1014 electrons/cm2), loss in common-emitter dc current gain of medium frequency n-p-n planar transistors at collector currents of one to 10 milliamperes is attributed to changes in the surface recombination velocity. Displacement-induced recombination centers in the base region cause a reduction in gain when ¿e is greater than 1014 electrons/cm2. A technique of saturating the surface damage with low energy electrons (E = 125 kev) so as to permit a separation of surface and bulk damage is demonstrated. The minority-carrier lifetime-damage constant, K¿, has been estimated from the separated bulk-damage curve. It agrees with the value determined from electron irradiation of a low frequency (f¿b = 1.25 Mc/sec) mesa n-p-n transistor which is shown to suffer degradation in gain only from bulk recombination current losses within the base region. Surface damage from both electrons and gamma rays is annealed at 250°C or by injecting emitter currents of 200 milliamperes which generate a high internal temperature. In contrast to this behavior, electron irradiation of p-n-p transistors caused loss in gain which is attributed to bulk damage. Damage constants, K¿, determined from the data show that p-n-p transistors suffer bulk radiation damage about five times greater than n-p-n transistors. View full abstract»

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  • Displacement Damage in MOS Transistors

    Page(s): 78 - 82
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    The changes in MOS device characteristics produced by neutron irradiation from the Northrop TRIGA reactor have been observed. Three damage mechanisms have been identified: an increase in net surface state density, a decrease in substrate resistivity, and a decrease in carrier mobility in the channel. The surface effect is usually dominant, although the bulk resistivity effect becomes increasingly important as the resistivity of the substrate is decreased. An exact closed form expression for the turn-on voltage has been derived by obtaining a solution to Poisson's equation in the gate region. The open circuit gate to substrate capacitance as afunction of gate to substrate voltage has been obtained by numerical integration techniques in terms of the charge density and dielectric constants present in the SiO2 layer and Si substrate. For both enhancement and depletion devices, an increase in positive charge density was apparent in the oxide region. It is postulated that the observedincrease in positive charge density is due to creation of mobile positive ions, and that the decreasing net accumulation rate with increasing flux is due to a diffusion or recombination process competing with the creation process. On this basis, a rate effect is expected. View full abstract»

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  • Radiation Induced Regeneration through the P-N Junction Isolation in Monolithic I/C's

    Page(s): 83 - 90
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    Some monolithic integrated circuits have been found to display a regenerative interaction between substrate parasitics and the intended semiconductor circuit elements when exposed to ionizing radiation. One manifestation of this effect can result in a bi-stable operating condition which prevents proper integrated circuit functioning until the power source is reduced. Experimental and analytic methods are described which have been used to determine the susceptibility of a specific type of monolithic integrated circuit to regenerative operation. The analytic methods predicting the form of the regenerative transient effect rely heavily on the use of an automated digital computer code termed Transient Radiation Analysis by Computer (TRAC) which mechanizes the complex nonlinear equations that simulate the semiconductor behavior. View full abstract»

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  • The Use of Lasers to Simulate Radiation-Induced Transients in Semiconductor Devices and Circuits

    Page(s): 91 - 100
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    High levels of ionization can be created in semiconductor devices by irradiating the devices with short pulses of light. If the light frequency is properly selected, sufficient and relatively uniform energy deposition is obtained which results in ionization rates orders of magnitude above those presently attainable from other sources. It is shown that a pulsed-infrared laser can be used as a relatively simple, inexpensive, and effective means of simulating the effects caused by intense gamma ray sources on semiconductors. Experimental results are presented which show that the transients induced in various types of silicon transistors when exposed to a neodymium laser are essentially identical to those obtained when the transistors are exposed to pulses of 25 MeV electrons from a linear accelerator and 600 kvp flash X-ray machine. Good agreement exists between the peak photocurrents obtained using these three sources over a dose range of 10-1 to 104 rads. Calculations based upon published as well as experimental absorption data for silicon show that energy deposition is very nearly uniform for the wavelength of light obtained from neodymium lasers (1. 06 microns - 1. 17 ev photons). By defocusing the laser light beam, dose rates in excess of 10R12 rads/ sec (silicon) in 40 x 1-99 seconds over an area of 50 cm2 have been obtained from a Q-switched 10 megawatt neodymium laser. This greatly exceeds the maximum dose rate of 1011< rads/ sec silicon) over approximately 1 c2m attainable from linear accelerators. View full abstract»

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  • Neutron and Gamma Sensitivities of Dynamic Detectors

    Page(s): 101 - 111
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    The neutron and gamma sensitivities of nine detectors were studied in experiments performed at the Sandia Pulsed Reactor (SPR). Of the detectors tested, six are predominantly gamma detectors at the SPR and three produce a significant fraction of their total current due to the neutron flux during a normal SPR burst. None of the detectors studied were found to be predominantly sensitive to the neutron flux during a normal SPR burst. Tests performed at pure gamma sources on a P-Intrinsic-N (PIN) diode detector are also described. The neutron induced current in the silicon detectors is treated theoretically. View full abstract»

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  • Calculation of Electrical and Radiation Storage Time in Transistors

    Page(s): 112 - 125
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    The conventional viewpoint of saturation in junction transistors, from a device point of view, considers the excess minority carriers in the base region. A different viewpoint considers the majority carriers in the base. The important elements then are the number of these carriers stored in the transistor and whether they are stored in the active base region, the extrinsic base region, the collector body, or the epitaxial layer. The storage of carriers in the active base region plays a relatively minor role in the storage effect for most modern transistors because of the small volume of semiconductor material involved. In alloy, diffused, and epitaxial transistors the storage of carriers (electrons in a PNP transistor) is shown to be in the last three regions named above, respectively; in none of these transistor types is the storage region identifiable as the active base region. This new viewpoint leads to well-accepted storage-time expressions for alloy and diffused transistors and to new storage-time expressions for epitaxial transistors. Detailed calculations of the primary photocurrent have been made for three practical transistor construction types that relate this current to basic device parameters and to the electrical storage time. In addition, the radiation storage time has been calculated in terms of the electrical storage time for epitaxial transistors. Examples of these calculations are given and the results presented. View full abstract»

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  • Effect of Operating Conditions and Transistor Parameters on Gain Degradation

    Page(s): 126 - 133
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    Data for predicting transistor gain degradation in a neutron radiation environment were obtained from experimental studies of the variation of the radiation damage constant KT as a function of temperature and current during both measurement and irradiation. Relatively small spreads in the values of KT were obtained when the individual base transit times were measured and the radiation exposures were precisely determined. Radiation damage effect data from 20 different n-p-n silicon transistor types were obtained and normalized to the same minority carrier concentration in the base region, using the transit time and the VBE-Ic characteristics of the specific transistors. The resulting relative dispersions of the damage constant for minority carrier densities of 1015/cm3 and 1016/cm3 were typically 15 to 20 percent. These dispersions indicate that electrical measurements of transistor physical parameters can provide reasonably accurate predictions of the gain degradation for a wide variety of transistors without additional radiation testing of specific transistor types. View full abstract»

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  • A Study of the Neutron-Induced Base Current Component in Silicon Transistors

    Page(s): 134 - 146
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    In a previous paper a neutron-induced component of base current was reported that increases in proportion to integrated neutron flux and varies with base-to-emitter voltage, VBE, as exp(q/nkT VBE), n being approximately 1.5. A component of base current which varies similarly with base-to-emitter voltage has previously been reported to be of surface-perimeter origin. For this reason it is significant to unambiguously locate the origin of the neutron-induced component. For this, a detailed study of the current-voltage characteristics, an analysis of the deviation of the characteristics from an exponential caused by emission concentration for "ring-dot" structures, and an analysis for the transverse bias dependence of the base current components for a special "tetrode-type" test structure were performed. The results indicate that the small "1.5 component" of current initially present is indeed of surface-perimeter origin while the added "1.5 component" of current induced by neutron bombardment is of bulk space charge region origin. To determine whether this effect is universal, an investigation was made of many different types of silicon transistors, and all were found to exhibit a similar neutron-induced current component. The number n in the exponential term is found to be a function of temperature decreasing with increasing temperature. For example at -50°C, n = 1.6, and at +100°C, n = 1.3. Annealing studies reveal an apparent difference in annealing rates for the neutral bulk base region and the high-field region of the emitter-base junction. View full abstract»

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  • Conference Awards

    Page(s): 155
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  • Affiliate Plan of the IEEE Nuclear Science Group

    Page(s): 155-a
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Aims & Scope

IEEE Transactions on Nuclear Science focuses on all aspects of the theory and applications of nuclear science and engineering, including instrumentation for the detection and measurement of ionizing radiation; particle accelerators and their controls; nuclear medicine and its application; effects of radiation on materials, components, and systems; reactor instrumentation and controls; and measurement of radiation in space.

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