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Changes induced by irradiation with 1.1 MeV protons in the transport properties and deep trap spectra of thick (>80 μm) undoped κ-Ga2O3 layers grown on sapphire are reported. Prior to irradiation, the films had a donor concentration of ∼1015 cm−3, with the two dominant donors having ionization energies of 0.25 and 0.15 eV, respectively. The main electron traps were located at Ec−0.7 eV. Deep acceptor spectra measured by capacitance-voltage profiling under illumination showed optical ionization thresholds near 2, 2.8, and 3.4 eV. The diffusion length of nonequilibrium charge carriers for ɛ-Ga2O3 was 70 ± 5 nm prior to irradiation. After irradiation with 1.1 MeV protons to a fluence of 1014 cm−2, there was total depletion of mobile charge carriers in the top 4.5 μm of the film, close to the estimated proton range. The carrier removal rate was 10–20 cm−1, a factor of 5–10 lower than in β-Ga2O3, while the concentration of deep acceptors in the lower half of the bandgap and the diffusion length showed no significant change.

The paper analyses the possibility to reduce the sensitivity of silicon integrated circuits (ICs) to single radiation effects by means of radiation-thermal treatment including irradiation in charged particle accelerators and subsequent low-temperature heat treatment. It is shown that reduction in sensitivity to single radiation effects is provided by formation of thermostable recombination centers in semiconductor IC structure in necessary concentrations. At the same time a decrease in primary photocurrent generated by heavy charged particles or high-energy protons, reduction in transfer coefficients of parasitic bipolar transistors forming thyristor structures, reduction in carrier avalanche multiplication coefficients at high electric field strengths can be provided. Radiationthermal treatment can be introduced in the manufacturing process of ICs of various classes at the end of the manufacturing cycle and does not require correction of the basic technology. A possible undesirable growth of inverse currents and preservation of values of other electrical parameters within acceptable values when using radiation-thermal treatment is provided by choosing optimal modes of irradiation and annealing which are established in the course of experimental tests. The calculated evaluation has shown that using radiation-thermal treatment in the technology of IC fabrication can provide a decrease in the effective collection length of non-equilibrium charge carriers generated under the influence of single radiation effects by at least 10 times which allows considering radiation-thermal treatment as an effective technological tool to suppress the sensitivity to single radiation effects.

The microstructures and the porosity parameters in vanadium alloys irradiated by helium ions are compared after preparing thin films from them for transmission electron microscopy (TEM) by two different techniques. V–1% Ti, V–1% Ta, V–2% Ta, and V–1% Ta–1% W alloy samples are subjected to annealing at 1000°C for 2 h and then to 40-keV helium ion irradiation to a fluence of 5 × 1020 m–2 at a temperature of 650°C. TEM samples are prepared by one-sided electrolytic thinning (ET) on the unirradiated side and by focused ion beam (FIB) cutting normal to the irradiated surface. The microstructures of the foil samples prepared by ET and FIB are shown to be significantly different, which leads to a discrepancy between the calculated porosity parameters and the irradiation-induced swelling. When samples are prepared by ET, the picture substantially depends on the material layer to be fixed, and the layer thickness and position are not controlled. Therefore, the use of ET samples leads increases the error of measuring the porosity parameters, and reproducibility of the results can hardly be reached in this case, which should be taken into account in investigations. Using FIB technique, one can measure the foil thickness in a scanning electron microscope during sample preparation, study the total swelling of the entire irradiated layer, and analyze the distribution of objects over the depth of an irradiated target along ion trajectories.

Films of α-Ga2O3 (Sn) grown by halide vapor phase epitaxy on sapphire with donor densities in the range 5 × 1015–8.4 × 1019 cm−3 were irradiated at 25 °C with 1.1 MeV protons to fluences from 1013 to 1016 cm−2. For the lowest doped samples, the carrier removal rate was ∼35 cm−1 at 1014 cm−2 and ∼1.3 cm−1 for 1015 cm−2 proton fluence. The observed removal rate could be accounted for by introduction of deep acceptors with optical ionization energies of 2 eV, 2.8 eV and 3.1 eV. For samples doped at 4 × 1018 cm−3, the initial electron removal rate was 5 × 103 cm−1 for 1015 cm−2 fluence and ∼300 cm−1 for 1016 cm−2 fluence. The same deep acceptors were observed in photocapacitance spectra, but their introduction rate was orders of magnitude lower than the carrier removal rate. For the heaviest doped samples, the electron removal rate was close to that for the 4 × 1018 cm−3 sample. The radiation tolerance of lightly doped α-Ga2O3 is higher than for similarly doped β-Ga2O3 layers.

The development of helium porosity in vanadium and its alloys with tungsten, zirconium, and tantalum during sequential ion irradiation by 40-keV He+ ions at 650°C to a fluence of 5 × 1020 m–2 and 20-keV H+ ions at 20°C to a fluence of 5 × 1020 m–2 is studied by transmission electron microscopy. The microstructure and the development of porosity in the alloys are investigated along the ion range. Unlike He+ ion irradiation, the alloying elements during sequential He+ and H+ ion irradiation increase the gas swelling of vanadium: tantalum causes the maximum swelling and zirconium minimum one. Gas bubbles in the tantalum-containing alloys are located at the depths that are significantly more than the calculated helium and hydrogen ion ranges. Deep penetration of introduced gas atoms is shown occur mainly along the grain boundaries that are perpendicular to the irradiated surface. The largest bubbles (gas-filled pores) during He+ ion irradiation are found to grow at the depth with a high radiation vacancy concentration rather than the maximum helium concentration. In sequential He+ and H+ ion irradiation, a zone with large pores forms more deeply, in the ion range zone, and large pores in the 100-nm-thick layer transforms into high-density small bubbles.

The results of an investigation of the development of porosity and swelling in the alloys V–Cr, V–W, V–Ta, and V–W–Ta irradiated by 40 keV helium ions to fluence 5·10 20 m – 2 at 650°C are presented. The investigations were conducted by means of transmission electron microscopy along the travel path of ions; this afforded some idea about the total swelling of the samples and the character of the depth distribution of the porosity in the targets. It was found that the gas swelling in binary alloys is identical to within the measurement error. Multicomponent alloying is effective from the standpoint of the suppression of helium swelling – the ternary alloy V–1%W–1%Ta is subjected to significantly less helium swelling. It observed for the first time in experiments that the distribution and penetration depth of helium ions different significantly from the calculations, and the effect depends strongly on the chemical composition of the irradiated alloy. Among the alloying elements tantalum promotes deeper penetration of helium ions. In addition, the effect increases with increasing concentration of tantalum in the alloy: in the alloys V–1%Ta and V–2%Ta, pores were discovered at depth 450–500 and 850–900 nm, respectively, which is significantly greater than the computed travel distance of 48 keV helium ions in vanadium (~300 nm).

Carbon implantation can be effectively used for axial minority charge carriers’ lifetime control in various silicon bulk and epitaxial planar structures. When carbon is implanted, more stable recombination centres are formed and silicon is not doped with additional impurities, as for example, when irradiated with protons or helium ions. Economically, such a process competes with alternative methods, and is more efficient for obtaining small lifetimes (several nanoseconds). I-3 ion injector with laser-plasma ion source at Institute for theoretical and experimental physics (ITEP) is used as ion implanter in semiconductors. The ion source uses pulsed CO2 laser setup with radiation-flux density of 1011 W/cm2 at target surface. The ion source produces beams of various ions from solid targets. The generated ion beam is accelerated in the two gap RF resonator at voltage of up to 2 MV per gap. Resulting beam energy is up to 4 MV per charge. Parameters of carbon ion beam generated and used for semiconductor samples irradiation during experiments for axial minority charge carriers lifetime control in various silicon bulk and epitaxial planar structures are presented.

The changes of electrical properties and deep trap spectra induced in n-type β-Ga2O3 by 1 GeV protons with a fluence of 4 × 1013 cm−2 were studied. The carrier removal rates were ∼100 cm−1 at this energy. For comparison, for 20 MeV proton irradiation at comparable fluences (5–10 × 1014 cm−2), the removal rate was ∼400 cm−1 for donor concentrations of 3 × 1016 cm−3 and ∼100 cm−1 for concentrations of

The effects of 20 MeV proton irradiation with fluences of 5 × 1014 and 1015 p/cm2 on electrical properties of lightly Sn doped n-type (net donor concentration 3 × 1017 cm−3) bulk β-Ga2O3 samples with (010) and (−201) orientation were studied. Proton irradiation decreases the net donor density with a removal rate close to 200 cm−1 for both orientations and similar to the electron removal rates in lightly Si doped β-Ga2O3 epilayers. The main deep electron traps introduced in the β-Ga2O3 crystals of both orientations are near Ec−0.45 eV, while in Si doped films, the dominant centers were the so-called E2* (Ec−0.75 eV) and E3 (Ec−0.1 eV) traps. Deep acceptor spectra in our bulk –Ga2O3(Sn) crystals were dominated by the well-known centers with an optical ionization energy of near 2.3 eV, often attributed to split Ga vacancies. These deep acceptors are present in a higher concentration and are introduced by protons at a higher rate for the (010) orientation. Another important difference between the two orientations is the introduction in the surface region (∼0.1 μm from the surface) of the (010) of a very high density of deep acceptors with a level near Ec−0.27 eV, not observed in high densities in the (−201) orientation or in Si doped epitaxial layers. The presence of these traps gives rise to a very pronounced hysteresis in the low temperature forward current–voltage characteristics of the (010) samples. These results are yet another indication of a significant impact of the orientation of the β-Ga2O3 crystals on their properties, in this case, after proton irradiation.

The electrical properties and deep trap spectra were compared for near-UV GaN/InGaN quantum well (QW) structures grown on free-standing GaN substrates. The structures differed by the presence or absence of a thin (110 nm) InGaN layer inserted between the high temperature GaN buffer and the QW region. Capacitance-voltage profiling with monochromatic illumination showed that in the InGaN underlayer (UL), the density of deep traps with optical threshold near 1.5 eV was much higher than in the QW and higher than for structures without InGaN. Irradiation with 5 MeV electrons strongly increased the concentration of these 1.5 eV traps in the QWs, with the increase more pronounced for samples without InGaN ULs. The observations are interpreted using the earlier proposed model explaining the impact of In-containing underlayers by segregation of native defects formed during growth of GaN near the surface and trapping of these surface defects by In atoms of the InGaN UL, thus preventing them from infiltrating the InGaN QW region. Deep level transient spectroscopy (DLTS) also revealed major differences in deep trap spectra in the QWs and underlying layers of the samples with and without InGaN ULs. Specifically, the introduction of the InGaN UL stimulates changing the dominant type of deep traps. Irradiation increases the densities of these traps, with the increase being more pronounced for samples without the InGaN UL. It is argued that light emitting diodes (LEDs) with InGaN UL should demonstrate a higher radiation tolerance than LEDs without InGaN UL. (C) 2020 Elsevier B.V. All rights reserved.

The influence of 60Co-irradiation accompanied by low-temperature treatment on AlGaAs/GaAs chips of 835 ± 25 nm superluminescent diodes (SLD) is addressed. It is shown that irradiation of potentially unreliable chips with latent defects in active 20-nm layer increases optical power degradation rate during the subsequent burn-in test. The possible cause of enhanced degradation of potentially unreliable chips during a long-term operation or gamma-ray irradiation is the presence of local defects, which can be rearranged into larger clusters commensurate with the active layer. The decrease in the degradation rate during the burn-in test for irradiated reliable chips probably caused by the mechanical stresses relaxation and its homogenization. A method for rejecting unreliable chips using gamma irradiation processing is proposed.

The results of an investigation of vacancy porosity and swelling development in the vanadium low-alloy V–0.3%Ti irradiated with 7.5 MeV Ni2+ ions at 650°C to damaging dose 100 dpa and with 40 keV He+ ions to fluence 5·1020 m−2 at 650°C and additionally with Ni2+ ions are presented. It is shown that at the maximum damage depth ~1.75 μm under irradiation with nickel ions the swelling equals 0.5%, which corresponds to the existing data and attests to the desirability of using the EPG-15 accelerator in simulation studies of the relative radiation resistance of the structural reactor materials at their pre-selection stage. Under irradiation of a sample in the sequence He+ + Ni2+ gas-filled pores form at depth considerably greater than the free-path of helium ions and swelling increases to 1.2% in the zone of maximum structural damage. Once the solubility limit is reached in vanadium the implanted nickel ions form 5–20 nm clusters.

Two types of near-UV light-emitting diodes (LEDs) with an InGaN/GaN single quantum well (QW) differing only in the presence or absence of an underlayer (UL) consisting of an InAlN/GaN superlattice (SL) were examined. The InAlN-based ULs were previously shown to dramatically improve internal quantum efficiency of near-UV LEDs, via a decrease in the density of deep traps responsible for nonradiative recombination in the QW region. The main differences between samples with and without UL were (a) a higher compensation of Mg acceptors in the p-GaN:Mg contact layer of the sample without UL, which correlates with the presence of traps with an activation energy of 0.06 eV in the QW region, (b) the presence of deep electron traps with levels 0.6 eV below the conduction band edge (E-c) (ET1) and at E-c 0.77 eV (ET2) in the n-GaN spacer underneath the QW, and the presence of hole traps (HT1) in the QW, 0.73 eV above the valence band edge in the sample without UL (no traps could be detected in the sample with UL), and (c) a high density of deep traps with optical ionization energy close to 1.5 eV for the LEDs without UL. Irradiation with 5 MeV electrons led to a strong decrease in the electroluminescence (EL) intensity in the LEDs without UL, while for the samples with UL, such irradiation had little effect on the EL signal at high driving current, although the level of driving currents necessary to have a measurable EL signal increased by about an order of magnitude. This is despite the 5 times higher starting EL signal of the sample with UL. Irradiation also led to the appearance in the LEDs with UL of the ET1 and HT1 deep traps, but with concentration much lower than without the UL, and to a considerable increase in the Mg compensation ratio.

Carrier removal rates and electron and hole trap densities in β-Ga2O3 films grown by hydride vapor phase epitaxy (HVPE) and irradiated with 18 MeV α-particles and 20 MeV protons were measured and compared to the results of modeling. The electron removal rates for proton and α-radiation were found to be close to the theoretical production rates of vacancies, whereas the concentrations of major electron and hole traps were much lower, suggesting that the main process responsible for carrier removal is the formation of neutral complexes between vacancies and shallow donors. There is a concurrent decrease in the diffusion length of nonequilibrium charge carriers after irradiation, which correlates with the increase in density of the main electron traps E2* at Ec − (0.75–0.78) eV, E3 at Ec − (0.95–1.05) eV, and E4 at Ec − 1.2 eV. The introduction rates of these traps are similar for the 18 MeV α-particles and 20 MeV protons and are much lower than the carrier removal rates.

Electron accelerator equipped with injection system and magnetic buncher to generate picoseconds pulsed beams (50 ps, 150 A, 10 MeV) prospective for radiation hardness investigation and pulsed detectors characterization is represented

The role of Shockley-Read-Hall non-radiative recombination centers on electroluminescence (EL) efficiency in blue multi-quantum-well (MQW) 436 nm GaN/InGaN light emitting diodes (LEDs) was examined by controlled introduction of point defects through 6 MeV electron irradiation. The decrease in the EL efficiency in LEDs subjected to irradiation with fluences above 5 × 1015 cm−2 was closely correlated to the increase in concentration of Ec-0.7 eV electron traps in the active MQW region. This increase in trap density was accompanied by an increase in the both diode series resistance and ideality factor (from 1.4 before irradiation to 2.1 after irradiation), as well as the forward leakage current at low forward voltages that compromise the injection efficiency. Hole traps present in the blue LEDs do not have a significant effect on EL changes with radiation because of their low concentration.

Irradiation with 6 MeV electrons of near-UV (peak wavelength 385–390 nm) multi-quantum-well (MQW) GaN/InGaN light emitting diodes (LEDs) causes an increase in density of deep electron traps near Ec−0.8 and Ec−1 eV, and correlates to a 90% decrease of electroluminescence (EL) efficiency after a fluence of 1.1 × 1016 cm−2. The likely origin of the EL efficiency decrease is this increase in concentration of the Ec −0.8 eV and Ec −1 eV traps.

Different proton irradiation regimes were tested to provide more than 20 kHz-frequency, soft reverse recovery "snap-less" behavior, low forward voltage drop and leakage current for 50 mm diameter 7 kA/400 V welding diode Al/Si/Mo structure. Silicon diode with such parameters is very suitable for high frequency resistance welding machines of new generation for robotic welding.

Radiation processing technologies for static and dynamic parameters modification of silicon bipolar semiconductor devices implemented. Devices of different classes with wide range of operating currents (from a few mA to tens kA) and voltages (from a few volts to 8 kV) were processed in large scale including power diodes and thyristors, high-frequency bipolar and IGBT transistors, fast recovery diodes, pulsed switching diodes, precise temperature- compensated Zener diodes (in general more than fifty 50 device types), produced by different enterprises. The necessary changes in electrical parameters and characteristics of devices caused by formation in the device structures of electrically active and stable in the operating temperature range sub-nanoscale recombination centres. Technologies implemented in the air with high efficiency and controllability, and are an alternative to diffusion doping of Au or Pt, γ-ray, proton and low-Z ion irradiation.

The electrical properties, electroluminescence (EL) power output and deep trap spectra were studied before and after 5 MeV electron irradiation of near-UV single-quantum-well (SQW) light-emitting diodes (LED) structures differing by the presence or absence of InAlN superlattice underlayers (InAlN SL UL). The presence of the underlayer is found to remarkably increase the EL output power and the radiation tolerance of LEDs, which correlates with a much lower and more slowly changing density of deep traps in the QW region with radiation dose, and the higher lifetime of charge carriers, manifested by higher short-circuit current and open-circuit voltage in current–voltage characteristics under illumination. The observed phenomena are explained by the capture of native defects segregated at the growing surface by In atoms in the underlayer which traps them in the underlayer and prevents their penetration into the QW region.