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Nuclear Science, IEEE Transactions on

Issue 6 • Date Dec. 1969

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Displaying Results 1 - 25 of 54
  • [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): 1 - 4
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  • The Nucleus

    Page(s): 5
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  • Summary of 1969 IEEE Annual Conference on Nuclear and Space Radiation Effects

    Page(s): 6
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  • Scenes at 1969 IEEE Radiation Effects Conference

    Page(s): 7
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  • IEEE Nuclear Science Group Radiation Effects Committee

    Page(s): 8
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  • Reviewers for Conference Issue - 1969

    Page(s): 9
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  • 1969 IEEE Conference Outstanding Paper Award

    Page(s): 10 - 11
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  • A Microscopic View of Radiation Damage in Semiconductors Using EPR as a Probe Invited Paper

    Page(s): 13 - 18
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    This is the text of a tutorial talk on the use of electron paramagnetic resonance (EPR) as a "microscopic" tool in the study of radiation-produced defects in semiconductors. The basic concepts of EPR and its general applicability to point defects in semiconductors are outlined. As an illustrative example, the study of a p-type (aluminum doped) silicon sample is described from 20.4°K irradiation with 1.5 MeV electrons through various annealing stages. By analysis of the EPR spectra, it is shown that the major defects can be identified and the annealing mechanisms determined. View full abstract»

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  • Impurity Dependence of Defect Introduction and Annealing in Electron Irradiated n-Type Germanium

    Page(s): 19 - 23
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    Electron irradiation experiments on Si and Ge have indicated the creation of highly mobile interstitial atoms that in turn displace substitutional chemical impurity atoms (S) from the lattice; hence, the primary products of irradiation may be lattice vacancies (V) and interstitial chemical impurities (I). Subsequent annealing may then involve some type of interaction between (V) and (I). The relative amount of radiation damage, or ratio of (I) to the remaining substitutional chemical impurity atom concentration (SR), is also expected to be of importance since there may be competition during annealing between (I) and (SR) for the mobile (V). Samples of P, As, Sb, Sb-Ag, and Sb-Au doped n-type Ge of different initial carrier concentrations were irradiated at ~ 295°K with ~ 1.7 Mev electrons to different ratios of (I) to (SR), and electrical property measurements were made at 77°K immediately after irradiation. The results indicate (1) an increase in the apparent rate of removal of conduction electrons for material of higher initial carrier concentration, (2) a difference in the apparent rate of removal for different dopants, (3) a small dependence of the apparent removal rate on the total amount of disorder introduced, and (4) the amount of annealing was not a sensitive function of the ratio of (I) to (SR) for P or Sb-doped material, but was for As-doped material. View full abstract»

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  • Interstitial Defects in p-Type Silicon

    Page(s): 24 - 27
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    Two defects introduced in boron- and aluminum-doped silicon by 1.5-MeV electron irradiation have been studied by means of infrared photoconductivity. The defects have been identified as being dopant atoms in interstital positions. Stress-induced dichroism measurements have allowed the determination of the defects' symmetry which is C3v. View full abstract»

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  • Thermal and Injection Annealing of Neutron-Irradiated p-Type Silicon between 76°K and 300°K

    Page(s): 28 - 32
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    Measurements of minority carrier lifetime damage constant and divacancy growth following neutron irradiation at 76°K have been used to characterize further the annealing of neutron damage in silicon below 300°K. It has been shown that electron injection into p-type silicon at 76°K causes recovery of the neutron induced defect clusters with the simultaneous appearance of divacancies. Comparison of isochronal annealing curves of damage constant taken with and without prior injection at 76°K illustrates the nature of cluster annealing below 300°K. The thermal annealing results are shown to agree with previous annealing measurements of the carrier removal rate. View full abstract»

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  • Annealing Studies of Damage Introduced by High Energy Ion Implantations of Silicon

    Page(s): 33 - 36
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    Ion implantation of dopant impurities into semiconductors offers numerous potential advantages. However, because of the limited knowledge presently available on the annealing of lattice damage, the implantation profile and the electrical characteristics of implanted layers, a considerable amount of investigation is required before this doping technique can be put to practical use. Experimentally obtained implantation profiles and electrical conductivity characteristics of high energy (above 1 Mev) dopant ion implants into silicon are presented. Some preliminary results of ion implantation on silicon dioxide and on the resulting devices are also included. View full abstract»

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  • Observation of Crystal Lattice Planes in Neutron and Ion Bombarded Ge Invited Paper

    Page(s): 37 - 42
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    In the present work a review of the acheivements of the Gossick and Crawford model of disordered regions in semiconductors is given, together with a transmission electron microscope investigation of the structural characteristics of the disordered regions themselves. Both diffraction contrast and phase contrast electron microscope images have been used to examine disordered regions observed in Ge irradiated with fast neutrons or 100 keV oxygen ions. Experimental evidence is presented which clearly demonstrates that the disordered regions have an amorphous rather than a defect rich crystalline structure. Furthermore, each disordered region is observed to be surrounded by a non-uniform strain field extending out to ~65Å from the disordered region center. View full abstract»

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  • Neutron Fluence and Electric Field Strength Dependencies of the Rate of Volume Damage Introduction in Silicon P-N Junctions

    Page(s): 43 - 52
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    The anamolous behavior of neutron-induced defect clusters in the high field space-charge region of silicon p-n junctions is investigated. The space-charge region recombination current variation with neutron fluence and the junction electric field strength present during irradiation is examined and an electric field strength dependence for the defect clusters is found to exist. The space-charge region rate of volume damage introduction is observed to be a function of both neutron fluence and the junction electric field strength present during irradiation. An empirical expresion for the dependence of the rate of volume damage introduction on fluence and junction field strength present during irradiation is developed. Possible mechanisms for the observed field dependence are discussed. View full abstract»

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  • Minority Carrier Recombination in Neutron Irradiated Silicon

    Page(s): 53 - 62
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    Measurements are reported which provide extensive data on the resistivity, temperature, and injection level dependences of the minority carrier lifetime in neutron irradiated p- and n-type silicon. The lifetime damage constants are observed to be quite dependent on the injected minority carrier density, in both conductivity types, over the temperature range from 76°K to 300°K. The low injection level damage constants have been measured and found to be dependent on material resistivity in p-type silicon, but only slightly dependent on resistivity in n-type silicon. The results of the experimental studies are compared to the predictions of two alternate models for recombination at defect clusters. For defect clusters of approximately 250 A radius, as expected from range calculations, these comparisons indicate that each contains a relatively small number of deep defects (30 - 40). The defects are individually characterized by a deep donor level near Ev + 0.35 eV and a deep acceptor level near Ec - 0.50 eV. Since these levels correspond approximately to the known energy levels of the silicon divacancy, it is suggested that the divacancy may be the active recombination center within the defect clusters. View full abstract»

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  • Impurity Effects on Transistor Behavior at Low Temperature

    Page(s): 63 - 68
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    Unusual low temperature behavior has been observed in NPN silicon transistors when gallium is employed as the base dopant. The current gain exhibits a pronounced "hump" near 76°K in these devices, which enables them to be studied and utilized at this low temperature. Near the hump temperature, the tolerance of the gallium doped devices to fast neutrons is observed to be approximately a factor of five greater than at room temperature. The peak in transistor gain at low temperature has been explained in terms of the change in emitter injection efficiency with temperature as a result of the different rates of carrier freeze-out in the base and emitter regions. In the model proposed, the increased radiation tolerance results from a decrease in the recombination in the emitter space charge region at low temperatures. View full abstract»

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  • Effect of 14 MeV Neutrons on Space-Charge-Limited Current of Electrons in High Purity Silicon

    Page(s): 69 - 80
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    Alloyed and symmetrical n+¿n+ devices made of nominally 75k¿cm ¿-type Si are analyzed before and after irradiation with 14MeV neutrons at room temperature and doses of 1.2×1011, 5.5×1011 and 4.0×1012n/cm2. Immediately after the application of a large turn-on voltage step at t ¿ O, the flow of electrons through these devices is by pure, trap free, space-charge-limited current (sclc). From an analysis of this sclc, it is established that the drift velocity-field relationship of electrons in Si is affected by the radiation only at low temperatures in the low field range. For t>0, the current after irradiation decays below its initial trap free sclc value, thus revealing the presence of traps. Two categories are identified: fast traps with energy levels at about ¿Etf ¿ 0.13eV below the conduction band and slow traps with energy levels at roughly ¿Ets¿005eV. Cross sections are also obtained. Introduction rates are about equal for both (llcm-l for fast traps and 8cm-1 for slow traps). These results demonstrate the sensitivity of sclc as a tool to detect traps and changes in the drift velocityfield relationship caused by radiation. Some implications of these results are discussed and additional experiments are suggested. View full abstract»

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  • Optimization of the Neutron Radiation Tolerance of Junction Field Effect Transistors

    Page(s): 81 - 86
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    The fast neutron irradiation induced degradation of junction field effect transistors has been studied in detail. A comparison of p-channel to n-channel devices has confirmed reported differences in hole and electron removal rates. The predicted increase of hardness with increasing channel dopant concentration is experimentally demonstrated, although channel dopant grading makes very heavily doped units difficult to attain in practice. Also, a device modification which allows attainment of breakdown voltages higher than those characteristic of the channel doping level is presented and experimentally verified. This modification made possible the construction of devices with breakdown voltages greater than fifty volts, which degraded by only 25% in transconductance at fluences of approximately l-3×1015 neutrons/cm2 (E > 10 kev, Triga). Thus, the technique offers promise in the construction of very radiation resistant devices with wide operating voltage ranges. View full abstract»

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  • Radiation Effects on Junction Field Effect Transistors

    Page(s): 87 - 95
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    Experimentally determined permanent and transient effects of radiation on the electrical characteristics of junction field effect transistors (JFET's) are presented for JFET's exposed to energetic neutron doses up to 1016 neutrons/cm2 (E > 10 Kev) and ionizing radiation up to 8×109 rad/sec. Results of extensive transient radiation experiments using the AFCRL Linac are presented for various combinations of channel doping, gate resistor values, gate voltages, drain voltages, gold doping and dose rates. Limited new experimental data is presented on neutron damage. Existing neutron degradation data on hardened JFET's is summarized. The JFET neutron degradation theory is summarized and refined. View full abstract»

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  • Radiation-Induced Integrated Circuit Latchup

    Page(s): 96 - 103
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    This paper discusses integrated circuit (IC) structures and associated physical mechanisms which are responsible for the phenomenon of radiation-induced latchup. Laboratory measurements on selected IC's haveverifiedthatthestructures described will support latchup. These measurements are briefly discussed. An important result of the laboratory measurements has been to establish that electrical tests can be used to identify latchup-prone structures within an IC. These measurements, together with an understanding of the biasing conditions that must exist in order to initiate the latchup path, can be used to determine the susceptibility of an IC, in normal operation, to radiation-induced latchup. A careful analysis of a given IC's topology can uncover all latchup-prone structures. Once such structures have been identified, appropriate electrical testing can be implemented during the IC production phase to determine the V-I characteristics of these paths. This procedure will supply the necessary information regarding the biasing conditions required for the initiation of the latchup paths when the IC is exposed to an ionizing radiation environment. One-hundred percent electrical testing may be required, depending upon the results of the analyses, in order to uncover the single latchup-prone individual, among several hundred IC chips, which might possess an anomalous V-I characteristic. It is concluded that four-layer (p-n-p-n) action is the primary latchup sustaining mechanism, while transistor sustaining voltage breakdown is of little concern and second breakdown is probably of minor importance for most IC's. Second breakdown must be given careful consideration, however, before a given IC can be considered to be latchup free. View full abstract»

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  • An Analysis of Ionizing Radiation Effects in Four-Layer Semiconductor Devices

    Page(s): 104 - 110
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    The switching of a four-layer semiconductor device in an ionizing radiation environment is calculated by solving the charge transport equations to determine the motion of the electron and hole distributions and the changes in the electric field distribution throughout a one-dimensional device as a function of time. A discussion of the characteristic device turn-on as a function of the ionizing radiation exposure and external circuit and device parameters is presented. In addition to showing the detailed calculated device behavior, the theoretical and experimental results are compared. View full abstract»

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  • Transient Radiation Response of Complementary-Symmetry MOS Integrated Circuits

    Page(s): 114 - 119
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    Complementary-symmetry MOS (CMOS) integrated circuits were subjected to a sub-microsecond burst of high intensity ionizing radiation using 10-MeV electrons from a LINAC. The results show that, at peak doserate values of less than 8 × 108 rads (Si)/s, the transient change in output voltage of a CMOS inverter is small and can be attributed simply to the net junction photocurrent flowing at the output node. At dose rates in excess of 8 × 108 rads (Si)/s, however, a new type of response comes into play and the transient change in output voltage becomes very large, approaching the operating voltage. In some instances, this change can result in a non-destructive temporary latch-up condition. The results suggest that this condition is caused by a parasitic effect, namely the interaction of the P-well, the source-drain diffusions, and the protection diodes that constitute a four layer structure. View full abstract»

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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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