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It has been shown that the interaction of 1 MeV protons at doses of (0.5–2) × 1014 cm–2 with transistor structures having a 2D AlGaN/GaN channel (AlGaN/GaN HEMTs) is accompanied not only by the generation of point defects, but also by the formation of local regions with a disordered nanomaterial. The degree of disorder of the nanomaterial was evaluated by multifractal analysis methods. An increase in the degree of disorder of the nanomaterial, manifested the most clearly at a proton dose of 2 × 1014 cm–2, leads to several-fold changes in the mobility and electron density in the 2D channel of HEMT structures. In this case, the transistors show a decrease in the source–drain current and an order-of-magnitude increase in the gate leakage current. In HEMT structures having an enhanced disorder of the nanomaterial prior to exposure to protons, proton irradiation results in suppression of the 2D conductivity in the channel and failure of the transistors, even at a dose of 1 × 1014 cm–2.

Electrical properties of defects formed in n-Si(FZ) following 8 and 15 MeV proton irradiation are investigated by Hall effect measurements over the wide temperature range of T ≈ 25 to 300 K. Close attention is paid to the damaging factor of proton irradiation, leaving aside passivation effects by hydrogen. The concept of defect production and annealing processes being accepted in the literature so far needs to be reconsidered. Contrary to expectations the dominant impurity-related defects produced by MeV protons turn out to be electrically neutral in n-type material. Surprisingly, radiation acceptors appear to play a minor role. Annealing studies of irradiated samples of such complex defects as a divacancy tied to a phosphorus atom and a vacancy tied to two phosphorus atoms. The latter defect features high thermal stability. Identification of the dominant neutral donors, however, remains unclear and will require further, more detailed, studies. The electric properties of the material after proton irradiation can be completely restored at T = 800°C.

The changes of the current–voltage characteristics and the uncompensated donor-impurity concentration (N d –N a ) in the base electrode of Schottky diodes and JBS diodes based on 4H-SiC have been studied upon their irradiation with 0.9-MeV electrons and 15-MeV protons. The carrier-removal rate was 0.07–0.15 cm–1 under electron irradiation and 50–70 cm–1 under proton irradiation. It was shown that the current–voltage characteristics of the devices under study remain rectifying at electron irradiation doses of up to ~1017 cm–2. It was demonstrated that the radiation hardness of the SiC-based devices under study substantially exceeds that of silicon p–i–n diodes with similar breakdown voltages.

У даній статті аналізуються особливості забезпечення захисту інформації, приймаючи до уваги суб'єктивну сторону даного процесу. Основною метою дослідження є розробка алгоритму аналізу та управління комплексною безпекою, котрий дозволить уніфікувати підходи до управління інформаційною безпекою. Безпека не існує сама по собі, у відриві від людини. Вона забезпечується для людини і нею ж оцінюється. Тому, поняття безпеки має не тільки об'єктивну, але й суб'єктивну сторону, оскільки оцінка її рівня проводиться в кінцевому підсумку людиною. Використання методів когнітивного моделювання дозволяє значно покращити процеси аналізу та управління безпекою телекомунікаційної системи. Переваги когнітивного підходу полягають у можливості моделювання слабоструктурованих (тих, що погано формалізуються) систем, які характеризуються неповнотою або невизначеністю знань про них. Застосування розробленого алгоритму дозволить фахівцям приступити до розробки відповідних обчислювальних процедур і модулів, які можуть бути в подальшому використовуватися при забезпеченні захисту телекомунікаційної системи. Результати досліджень будуть також корисні службам, які займаються забезпеченням інформаційної безпеки.

Hall effect and conductivity measurements are taken on Si1 − x Ge x of n- and p-type at x ≤ 0.05. Much attention is given to electrical measurements over a temperature interval of 25 to 40 K where the mobility of charged carriers is strongly affected by alloy scattering. The partial mobility of electrons and holes due to this scattering mechanism is estimated for n-Si1 − x Ge x and p-Si1 − x Ge x at small x. Together with this, an effect of the presence of Ge atoms upon the ionization energy of phosphorus and boron impurities is investigated. Some points related to an inhomogeneous distribution of Ge atoms in Si1 − x Ge x are discussed.

The present experiments using fast electron and gamma-irradiation are aimed at checking the model of defect formation in oxygen-lean n-Si(FZ) in a quantitative way. Electrical measurements are taken over a wide temperature range of 20 to 300 K. Analysis of equations of charge balance making use of the statistics of charge carriers in non-degenerate semiconductors demonstrates that group-V impurity atoms strongly interact with intrinsic point defects. As a result, the concentration of shallow donor states is markedly decreased. This loss of shallow donors, −δND, is accompanied with an increase in the concentration of radiation-produced deep acceptors, +δNArad, being equal in magnitude but opposite in sign. Such behavior correlates quantitatively with the formation model of donor-vacancy pairs put forward earlier by Watkins and Corbett, what has been proved on the basis of electrical data for the first time. The formation kinetics of these complexes is discussed. Defects of interstitial type in irradiated material appear to be electrically neutral in n-Si. However, their production in the course of electron- and gamma-irradiation is believed to be responsible for drastic changes in the mobility of charge carriers at cryogenic temperatures.

The temperature dependence of photoluminescence (PL) in the range 8–300 K is studied for single crystalline silicon irradiated by protons at high temperatures. It is shown that the samples with p-type conductivity display intense PL in contrast to the samples with n-type conductivity, which do not display photo-luminescence. Studies using high-resolution transmission electron microscopy (TEM) have shown that photoluminescence exists until crack formation and splitting of the irradiated layer. The rodlike defects {113} formed during irradiation transform into residual fragments of dislocation structures.

Rates of carrier removal from the conduction band in n-type FZ-Si and 4H-SiC irradiated with 8- and 15-MeV protons at room temperature are discussed. Calculated rates of formation of primary radiation defects (Frenkel pairs) in these materials are presented and compared with the corresponding experimental values. Protons create defects in collision cascades involving recoil atoms formed in the crystal lattice itself. The results are compared with similar data previously obtained in irradiation of n-type FZ-Si and 4H-SiC with 900-keV electrons, in which case isolated so-called close Frenkel pairs are absolutely dominant among primary radiation defects. It has been found that the E-center model adequately describing the decrease in the electrical conductivity of n-FZ-Si upon electron irradiation is inapplicable to interpretation of experimental data for proton-irradiated materials. It is suggested that a pronounced annealing of “simple” radiation defects of the type of close Frenkel pairs occurs during irradiation at room temperature.

Radiation-produced defects in doped and nominally undoped n-GaN with charge carrier concentrations in a range of 4 × 10 16 cm -3 to about 2 × 10 18 cm -3 are investigated. Layers of n-GaN are irradiated with fast electrons at 0.9 MeV, 60 Co gamma rays and protons at 150 keV. The production rates of radiation defects in n-GaN are estimated and compared with literature data. Annealing processes of radiation defects in n-GaN in the temperature range 100-700 °C are also discussed. The annealing behavior appears to be complicated. Two temperature intervals, from T= 100 to 400°C and from T = 500 to 700°C, are characteristic for modification and annealing processes of radiation-produced defects in n-GaN.

Effects of proton irradiation on the optical and electrical properties of n-InN with charge carrier concentrations of 2 - 5 x 10 18 cm -3 have been investigated. Strong changes in photoluminescence spectra and electrical parameters of irradiated n-InN are discussed. Proton irradiation of n-InN results in the appearance of shallow donors in large concentrations. Comparison with the effects observed on heavily degenerate n-InN after proton irradiation leads to the conclusion that these irradiation-produced donors are native defects, most likely vacancies on the nitrogen sublattice.

Nuclear-particle detectors based on SiC with a structure composed of an n+-type substrate, a p-type epitaxial layer, and a Schottky barrier are studied. Structures with a ∼10-µm-thick 6H-SiC layer exhibit transistor properties, whereas those with a ∼30-µm-thick 4H-SiC layer exhibit diode properties. It is established that a more than tenfold amplification of the signal is observed in the transistor-type structure. The amplification is retained after irradiation with 8-MeV protons with a dose of at least 5×1013 cm−2; in this case, the resolution is ≤10%. Amplification of the signal was not observed in the structures of diode type. However, there were diode-type detectors with a resolution of ≈3%, which is acceptable for a number of applications, even after irradiation with the highest dose of 2×1014 cm−2.

It is shown that irradiation of Ni-SiC structures with protons at elevated temperatures promotes metallurgical reactions at the Ni-SiC interface owing to a diffusion mechanism stimulated by the generation of radiation defects. The most pronounced effect of mixing at the metal-semiconductor interface is observed if the thickness of the metal film is equal to the projected range of protons.

Production processes of electrically active defects in nominally undoped n-GaN irradiated with fast electrons are investigated. It has been demonstrated that the silicon impurity atoms with shallow donor states at EC – 20 meV interact with native defects neither during irradiation nor annealing at elevated temperatures. Two major kinds of defects produced by irradiation in n-GaN are revealed: donor centers at EC – 70 meV and deep acceptors centers. These defects were found to be unstable at T > 200 °C. They can be attributed to the vacancies on the nitrogen and gallium sublattices, respectively.

Buried nanoscale damaged layers formed in Si and SiC crystals via 50-and 100-keV proton implantation were studied. It is shown that the sensitivity of atomic-force microscopy is sufficiently high to detect the initial stages of the development of hydrogen-containing voids and microcracks in subsurface layers of irradiated crystals and to study exfoliation of the crystals in the plane of microcracks. As a result, quantitative criteria for the formation of buried damaged layers in the studied crystals were derived; also, the conditions for blistering and for implementation of the “Smart-Cut” technology were determined.

It is shown that the axial distribution of the recombination center concentration in high-voltage silicon p+Nn+ diodes can be controlled by electron irradiation in a certain energy range. Results of investigations of the main static and dynamic characteristics of electron-irradiated diodes are presented.

The electrical properties of the n-GaN and n-InN, subjected to proton irradiation, are studied. The irradiation of the n-InN results in an increasing concentration of charge carriers, whereas strong compensation effects take place in the proton-irradiated n-GaN. The annealing behavior of the radiation-induced defects in both materials is discussed briefly.

The p+-n-n+ structures based on 6H-SiC films grown by chemical vapor deposition on the n+ substrate were irradiated with 8-MeV protons with a dose of 8×1015 cm−2. In order to stabilize the material, it was annealed for 10 min at 450°C. As a result, the resistivity of the film was ρ=5×109 Ω cm. The effect of proton irradiation was studied by alpha spectrometry. The 5.77-MeV alpha particles were detected for both reverse and forward bias voltages applied to the structure. The results of the following two modes of detection were compared: (i) a particle traverses the structure without losing much of its energy, and (ii) a particle is stopped in the structure. It is shown that, in the former case and under a forward bias, a signal is formed by a mechanism involving a “through-conducting channel.” This makes it possible to determine the product of lifetime of electrons by their mobility. The situation in which the particle range R does not exceed the film thickness was analyzed; this situation is typical of spectrometry. It is noted that a decrease in R results in different behavior of the signal for the bias voltages of opposite polarity. Thus, for forward bias, the signal amplitude decreases more rapidly and for larger values of R.

Capacitance-related methods and electron spin resonance were used to study the deep-level centers formed in n-4H-SiC as a result of irradiation with 8-MeV protons. For the samples, Schottky diodes and p-n structures formed on the layers either obtained by sublimational epitaxy or produced commercially by CREE Inc. (United States) were used. It was found that the type of centers introduced by irradiation is independent of the technology of the material growth and the type of charged particles. On the basis of the results of annealing the defects and the data of electron spin resonance, the possible structure of the centers is suggested.

Capacitance methods and electron spin resonance (ESR) were applied to study deep centers in n-6H-SiC irradiated with 8 MeV protons. Schottky diodes and p-n structures grown by sublimation epitaxy or commercially produced by CREE Inc. (United States) were used. The type of the irradiation-induced centers is independent of the material fabrication technology and the kind of charged particles used. Irradiation results in an increase in the total concentration of donor centers. The possible structure of the centers is suggested on the basis of data on defect annealing and ESR.

Analysis is given of the progress in the modification of semiconductors by proton beams in fields such as proton-enhanced diffusion, ion-beam mixing, and formation of porous layers. This method of modification (doping) is shown to have high potential in monitoring the properties of semiconductor materials and designing devices of micro and nano electronics as compared to the conventional doping techniques such as thermal diffusion, epitaxy, and ion implantation.

Radiation-induced point defects and their annealing in silicon-doped n-GaN have been investigated by means of Hall effect measurements and Raman spectroscopy. Correlated compensation effects due to simultaneous introduction of donor and acceptor centres are observed in irradiated n-GaN. The defect production rate is dependent on the dopant concentration. This means that the model of all native defects immobile at room temperature is not true. The behaviour of radiation-induced defects upon heating is complicated, exhibiting two prominent stages of reverse annealing. The presence of radiation defects is still observable after annealing to T = 750 °C.

Formation and annealing of radiation-induced defects in doped and nominally undoped n-GaN are investigated by means of electrical measurements and Raman spectroscopy. The production rate of defects turned out to be dependent on the dopant concentration. This suggests that at least one kind of native defects is involved in impurity–defect interactions at room temperature. Two prominent stages of defect annealing are revealed. The annealing processes at T ≥100°C are associated with mobile native defects. A considerable fraction of radiation defects is still present in the materials after annealing to T ≥750°C.

A study has been made of the concentration profiles of radioactive isotopes produced by transmutation in the YBa2Cu3O7−x superconductor and PbZr0.54Ti0.46O3 ferroelectric by energetic protons (10 and 15 MeV), deuterons (4 MeV), and 3He and 4He nuclei (20 MeV). Profiles of two types have been observed: monotonic and with a maximum. It is shown that the type of isotope concentration profile is determined by the nature of the cross-section energy dependence of the nuclear reaction producing a given isotope.

Profiles of radioactive isotopes produced in nuclear reactions in germanium irradiated by protons or 4He nuclei were studied. The profiles were used to determine the energy dependence of the cross sections of nuclear reactions producing transmutation isotopes.

The method of spin-dependent recombination was used to record electron spin resonance (ESR) spectra of recombination centers in a thin (∼1 µm) surface layer of p-type silicon grown by the Czochralski method and irradiated by protons with energies of ∼100 keV. Spectra of excited triplet states of the oxygen + vacancy complex (A-centers) were observed along with complexes consisting of two carbon atoms and an interstitial silicon atom (CS-SiI-CS complexes). The intensity of the ESR spectra of these radiation-induced defects was found to be largest at irradiation doses of ∼1013 cm−2, and decreased with increasing dose, which is probably attributable to passivation of the radiation-induced defects by hydrogen.

Nuclear doping due to charged particles (protons and α-particles) in GaAs and InP is analysed. The analysis results in the conclusion about the donor and acceptor doping efficiency by irradiation. The nuclear doping process is investigated by the compact cylclotron MGC-20, proton and α-particle energies being about 15 to 20 MeV. It is shown that the most effective nuclear doping of gallium arsenide and indium phosphide is achieved with donor impurities (selenium, germanium for GaAs and sulphur, tin for InP) by α-particle irradiation. Kerndotierung durch geladene Teilchen (Protonen und α-Teilchen) in GaAs und InP wird untersucht. Die Analyse gibt Hinweise fur die Donator- und Akzeptor-Dotierungseffizienz durch Bestrahlung. Der Kerndotierungsprozes wird mittels Zyklotron MGC-20 untersucht, wobei die Energien der Protonen und α-Teilchen bei etwa 15 bis 20 MeV liegen. Es wird gezeigt, das die effektivste Kerndotierung von GaAs und InP mit Donatorstorstellen (Selen, Germanium fur GaAs und Schwefel, Zinn fur InP) durch α-Teilchenbestrahlung erreicht wird.

This paper reports on the radiation resistance of In/sub 0.53/Ga/sub 0.47/As (InGaAs) cells with a p/n configuration. These solar cells can be used as bottom cells in high-efficiency tandems with wide gap top cells and as thermophotovoltaic converters. The cells designed for this study were fabricated by diffusion of Zn into undoped layers grown by liquid phase epitaxy (LPE). Cells with a total area of 0.16 cm/sup 2/ were used to carry out these measurements. After 1-MeV electron irradiation at a fluence level of 1/spl times/10/sup 16/ cm/sup -2/, the following values were typically found in the samples used for this study. V/sub OC/=0.26-0.29 V; J/sub SC/=38-40 mA/cm/sup 2/; FF=0.59-0.60; efficiency=4.2-4.5% (AM0, 1 Sun).

A new method is proposed for determining the energy losses of charged particles in solids, which is based on the comparison of profiles of the transmutation isotopes measured in the samples irradiated by particles of various energies.

The distribution of hydrogen in Si and SiC following high-temperature proton irradiation (Tirr=20–700 °C) is studied by secondary-ion mass spectrometry. It is shown that the hydrogen concentration profile in SiC depends weakly on irradiation temperature. In Si appreciable alteration of the concentration profile is observed already at Tirr⋍300 °C, and the profile completely loses its concentration gradient at Tirr⋍700 °C.