Effects Of High-energy Proton Irradiation Research Articles

Study of High-Energy Proton Irradiation Effects in Top-Gate Graphene Field-Effect Transistors

In this article, the effects of high-energy proton irradiation on top-gate graphene field-effect transistors (GFETs) were investigated by using 20 MeV protons. The basic electrical parameters of the top-gate GFETs were measured before and after proton irradiation with a fluence of 1 × 1011 p/cm2 and 5 × 1011 p/cm2, respectively. Decreased saturation current, increased Dirac sheet resistance, and negative drift in the Dirac voltage in response to proton irradiation were observed. According to the transfer characteristic curves, it was found that the carrier mobility was reduced after proton irradiation. The analysis suggests that proton irradiation generates a large net positive charge in the gate oxide layer, which induces a negative drift in the Dirac voltage. Introducing defects and increased impurities at the gate oxide/graphene interface after proton irradiation resulted in enhanced Coulomb scattering and reduced mobility of the carriers, which in turn affects the Dirac sheet resistance and saturation current. After annealing at room temperature, the electrical characteristics of the devices were partially restored. The results of the technical computer-aided design (TCAD) simulation indicate that the reduction in carrier mobility is the main reason for the degradation of the electrical performance of the device. Monte Carlo simulations were conducted to determine the ionization and nonionization energy losses induced by proton incidence in top-gate GFET devices. The simulation data show that the ionization energy loss is the primary cause of the degradation of the electrical performance.

Effects of 5 MeV proton irradiation on 4H-SiC lateral pMOSFETs on-state characteristics

Silicon carbide (SiC) MOSFETs are often used in harsh environments where they are exposed to ionizing radiation. This paper investigates the effects of high-energy proton irradiation on SiC MOSFETs, with a particular emphasis on the on-state characteristics of lateral pMOSFETs. By comparing with the lateral 4H-SiC nMOSFET after irradiation in our prior work, we observed the deviations of important electrical parameters. As the irradiation dose increases, the threshold voltage (VTH) of pMOSFETs is negatively shifted and has more negative offsets than that of nMOSFETs. This is due to two factors which affect VTH after irradiation: the near interface oxide traps (NIOTs) and the interface traps (Nit). These two factors compensate each other for nMOSFETs, but strengthen each other for pMOSFETs. It is found that an increase in the density of interface traps (Dit) in both types of MOSFETs after irradiation. However, unlike the nMOSFET, the pMOSFET has a decreasing field effect mobility (μFE) with the increase of irradiation dose. We believed that besides the effect of Dit on μFE, NIOTs have a more profound influence on μFE, resulting in different changes between nMOSFETs and pMOSFETs’ μFE.

The impacts of localized backside etching on proton radiation response in SOI passive devices

In this work, the effect of high-energy proton irradiation on the radiofrequency (RF) properties of silicon-on-insulator (SOI) substrates is investigated. The localized backside etching (LBE) structure is introduced for RF properties improvement and proton irradiation hardening. It is observed that after the 50 MeV proton irradiation with a fluence of 1 × 1012 p cm−2, the attenuation, crosstalk, and relative permittivity significantly decrease for conventional SOI substrates. In contrast, LBE substrates are less sensitive to proton irradiation and simultaneously exhibit better RF performance. The enhancement of the LBE structure on irradiation tolerance is qualitatively characterized by the equivalent circuit model parameter extraction.

Impact of 100 MeV high-energy proton irradiation on β-Ga2O3 solar-blind photodetector: Oxygen vacancies formation and resistance switching effect

β-Ga2O3 based solar-blind photodetectors have strong radiation hardness and great potential applications in Earth's space environment due to the large bandgap and high bond energy. In this work, we investigated the photoelectric properties influence of β-Ga2O3 photodetector irradiated by 100 MeV high-energy protons which are the primary components in the inner belt of the Van Allen radiation belts where solar-blind photodetectors mainly worked. After proton irradiation, due to the formation of more oxygen vacancies and their migration driven by bias at the metal/semiconductor interface, transportation of carriers transforms with electron tunneling conduction for low-resistance state and thermionic emission for high resistance state. As a result, the current–voltage curves of β-Ga2O3 solar-blind photodetectors exhibit apparent hysteresis loops. The photoresponsivity of β-Ga2O3 photodetectors slightly increases from 1.2 × 103 to 1.4 × 103 A/W after irradiation, and the photoresponse speed becomes faster at a negative voltage while slower at positive voltage. The results reveal the effects of high-energy proton irradiation on β-Ga2O3 solar-blind photodetectors and provide a basis for the study of their use in a radiation harsh environment.

MeV proton irradiation damage in Ta: Measurements, characterization and comparison to W

The effects of high-energy proton irradiation on tantalum and its properties, were studied at the Soreq Applied Research Accelerator Facility (SARAF) using a high-flux 2.2 MeV proton beam. Samples were characterized by optical interferometry, nano-indentation and Time of Flight Secondary Ion Mass Spectrometry (ToF-SIMS), to study the effect of radiation damage. The experimental data on the penetration depth of 2.2 MeV protons in tantalum was found to be in good agreement with simulations and an increase of the irradiated sample’s hardness was measured. The volume expansion was found to be correlated to the total proton fluence. With the aid of density functional theory estimates of the point defect formation volumes, we suggest that hydrogen occupies mainly interstitial sites in the Ta lattice. We observed extensive diffusion of the hydrogen into the material. Thus, no blistering was observed up to a total fluence of 1.9•10 20 P/cm 2 , extending the lower bound for blister formation in tantalum to one to three orders of magnitude above the critical fluence for blistering in tungsten. A reaction-diffusion model was employed to analyze the spatial distribution of the point defects, to assist in the interpretation of the results in comparison with tungsten, and to identify the role of the hydrogen diffusion. We conclude that tantalum is a promising structural material in proton radiation environments.

High-energy proton irradiation effects on GaN hybrid-drain-embedded gate injection transistors

The characterization of commercial-grade power transistors upon high levels of particle irradiation is required to enable radiation tolerant LED power supplies for the new luminaires of CERN accelerator tunnels, which represent a harsh environment for semiconductor devices. This work describes the effects of 24 GeV/c proton irradiation on commercial GaN hybrid-drain-embedded gate injection transistors (HD-GITs) after a fluence of 5.9 × 1014 p/cm2. Measurements of drain leakage current, threshold voltage and Ids − Vds curves show that only a minor variation occurs in the electrical properties of GaN HD-GITs after the considered fluence; for example, an average increase of ≈11–13 mV is found in the threshold voltage upon irradiation. We also put forward a physical explanation of the observed degradation caused by proton irradiation; in particular, the electron drift velocity in the 2DEG channel at high electric fields appears to decrease due to a radiation-induced increase in phonon relaxation rate. Finally, an AC/DC LED power supply with current control using GaN HD-GITs is proposed for the new luminaires of CERN tunnels, meeting the requirements in terms of radiation hardness and light quality.

High-Energy Proton-Irradiation Effects on the Magnetism of the Transition-Metal Dichalcogenide MoS2

We have studied the effects of high-energy proton irradiation on the magnetism of the transition-metal dichalcogenide MoS2. The pristine sample showed ferromagnetic and paramagnetic responses with a diamagnetic background, which all decreased initially with increasing irradiation dose. The ferromagnetic component increased subsequently with further irradiation, for which a spin-3/2 species was identified from the analysis of the M(H) curve, in contrast to the spin-1 species identified in the pristine sample. The magnetism in our MoS2 samples may be accounted for by the structural defects that apparently are cured by low-dose proton irradiation and subsequently become significant by further irradiation.

Effects of high-energy proton irradiation on separate absorption and multiplication GaN avalanche photodiode

The effect of high-energy proton irradiation on GaN-based ultraviolet avalanche photodiodes (APDs) is investigated. The dark current of the GaN APD is calculated as a function of the proton energy and proton fluences. By considering the diffusion, generation–recombination, local hopping conductivity, band-to-band tunneling, and trap-assisted tunneling currents, we found that the dark current increases as the proton fluence increases, but decreases with increasing proton energy.

Effects of high-energy proton irradiation on the superconducting properties of Fe(Se,Te) thin films

In this paper we explore the effects of 3.5 MeV proton irradiation on Fe(Se,Te) thin films grown on CaF2. In particular, we carry out an experimental investigation with different irradiation fluences up to 7.30 · 1016 cm−2 and different proton implantation depths, in order to clarify whether and to what extent the critical current is enhanced or suppressed, what are the effects of irradiation on the critical temperature, resistivity, and critical magnetic fields, and finally what is the role played by the substrate in this context. We find that the effect of irradiation on superconducting properties is generally small compared to the case of other iron-based superconductors. The irradiation effect is more evident on the critical current density Jc, while it is minor on the transition temperature Tc, normal state resistivity ρ, and on the upper critical field Hc2 up to the highest fluences explored in this work. In more detail, our analysis shows that when protons implant in the substrate far from the superconducting film, the critical current can be enhanced up to 50% of the pristine value at 7 T and 12 K; meanwhile, there is no appreciable effect on critical temperature and critical fields together with a slight decrease in resistivity. On the contrary, when the implantation layer is closer to the film–substrate interface, both critical current and temperature show a decrease accompanied by an enhancement of the resistivity and lattice strain. This result evidences that possible modifications induced by irradiation in the substrate may affect the superconducting properties of the film via lattice strain. The robustness of the Fe(Se,Te) system to irradiation-induced damage makes it a promising compound for the fabrication of magnets in high-energy accelerators.

The effects of high-energy proton irradiation on the electrical characteristics of Au/Ni/4H-SiC Schottky barrier diodes

Au/Ni (20:80) Schottky barrier diodes (SBDs) were resistively evaporated on nitrogen-doped n–type 4H-SiC. Current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the SDBs were investigated before and after bombardment with 1.8MeV proton irradiation at a fluence of 2.0×1012cm–2. The measurements were carried out in the temperature range 40–300K in steps of 20K. Results obtained at room temperature (300K) showed highly rectifying devices before and after bombardment. It was observed that the proton irradiation induced an increase of ideality factor from 1.05 to 1.13, a decrease in Schottky barrier height from 1.40 to 1.22eV, an increase in series resistance from 10 to 66 Ω and a noticeable increase of the saturation current from 3.0×10–21 to 6.8×10–17A. The increase in saturation current after proton irradiation was attributed to the presence of interfacial states created by irradiation-induced defects. Thermionic emission dominated the I-V characteristics in the temperature range 120–300K but the I-V characteristics deviated from thermionic emission theory at temperatures below 120K for devices both before and after irradiation. The variation of the SBDs characteristics with temperature was attributed to the presence of lateral inhomogeneities of the SBH. Modified Richardson constants were determined from a Gaussian distribution of barrier heights to be 133 and 165Acm–2K–2 before and after irradiation, respectively.

High-energy proton-irradiation effects on the charge transport and electric dipole moment of KH2PO4

We have studied the charge transport and dielectric properties of KH2PO4 (KDP) single crystals, irradiated by proton beams with high energies up to 20 MeV, by means of the temperature-dependent electrical conductivity and dielectric constant measurements. It is shown that the electrical conductivity and the electric dipole moment may be sensitively controlled by the proton irradiation energy and dose. The activation energy and the dipole moment were shown to be strongly correlated.

Radiation hardness of the electrical properties of carbon nanotube network field effecttransistors under high-energy proton irradiation

The effect of high-energy proton irradiation on the physical properties of carbon nanotubes(CNTs) was investigated. The focus of the study was on the electrical properties ofsingle-walled carbon nanotube (SWNT) network devices exposed to proton beams.Field-effect transistors (FETs) of network type were fabricated using SWNTs andwere then irradiated by high-energy proton beams of 10–35 MeV with a fluence of4 × 1010–4 × 1012 cm−2 that are comparable to the aerospace radiation environment. The electrical properties ofboth metallic and semiconducting CNT network FET devices underwent no significantchange after the high-energy proton irradiation, indicating that the CNT network devicesare very tolerant in proton beams. Raman spectra confirm the proton-radiation hardness ofCNT network FET devices. The radiation hardness of CNT network FET devices promisestherefore the potential usefulness of CNT-based electronics for future space application.

High-energy proton irradiation effects in GaAs devices

In this paper, we compare the energy dependences (53 and 115 MeV) of proton displacement damage coefficients for p/sup +/n GaAs solar cells with previously reported calculations of nonionizing energy loss (NIEL). Deep level transient spectroscopy (DLTS) was used to generate damage coefficients from the introduction rates of defects. New damage coefficients generated from GaAs bulk LEDs light output (1-530 MeV) are also reported. The damage coefficients from these devices for proton energies E>10 MeV vary but are bounded by the total and Coulombic NIEL.

High-energy proton irradiation effects on tunnelling MOS capacitors

The conduction characteristics of MOS capacitors with thin gate oxide irradiated with high-energy protons have been studied. An excess current appears at low electric fields that can be explained with a trap-assisted tunnel model with a single trap level. By using devices with different areas it has been confirmed that this leakage current is uniformly distributed over the oxide area. In addition, a series resistance effect is revealed at high current levels, which increases with proton fluence. It is also shown that the damage induced by irradiation in the SiO 2/Si interface is negligible.

Effects of high-energy proton irradiation on the density and Hall mobility of majority carriers in single crystalline n-type CuInSe2 thin films

Proton irradiation effects in CuInSe2 (CIS) thin films have been investigated as a function of proton energy (0.38, 1 and 3 MeV). Single crystalline n-CIS thin films were prepared by radio frequency sputtering. The electrical properties of as-grown and irradiated samples were measured. The typical electron concentration and Hall mobility in as-grown samples were 4 × 1016 cm−3 and 120 cm2/Vs, respectively. After 0.38 and 1MeV proton irradiation, both of the electron concentration and Hall mobility were decreased as the fluence exceeded 1 × 1013 cm−2, but for 3 MeV proton irradiation, they were decreased over the fluence of 1 × 1014 cm−2. The damage by high-energy proton irradiation was lower than that by low-energy proton irradiation. The carrier removal rate with proton fluence was estimated about from 1800 to 300 cm−1 as proton energy was changed from 0.38 to 3 MeV. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Effect of High-Energy Proton Irradiation on DC Characteristics and Current Collapse in MgO and Sc[sub 2]O[sub 3] Passivated AlGaN/GaN HEMTs

MgO or Sc 2 O 3 passivated AlGaN/GaN high electron mobility transistors (HEMTs) were irradiated with 40 MeV protons at a dose equivalent to ∼10 years in low-earth orbit. Very little change in drain-source current, transconductance, or diode ideality factor was observed under these conditions, but the reverse breakdown increased due to a decrease in channel electron density. In addition, no significant change was observed in the drain-source current under pulsed conditions, indicating that the proton irradiation did not alter the effectiveness of the MgO and Sc 2 O 3 in passivating surface states.

5–20 MeV proton irradiation effects on GaAs/Ge solar cells for space use

This paper reports the high-energy proton irradiation effects on GaAs/Ge space solar cells. The solar cells were irradiated by protons with energy of 5–20 MeV at a fluence ranging from 1×10 9 to 7×10 13 cm −2 , and then their electric parameters were measured at AM0. It was shown that the I sc , V oc and P max degrade as the fluence increases, respectively, but the degradation rates of I sc , V oc and P max decrease as the proton energy increases, and the degradation is relative to proton irradiation-induced defect Ec−0.41 eV in irradiated GaAs/Ge cells.

High-energy proton irradiation effects on AlGaN/GaN high-electron mobility transistors

AlGaN/GaN high-electron mobility transistors (HEMTs) show decreases in extrinsic transconductance, drain-source current threshold voltage, and gate current as a result of irradiation with 40 MeV protons at doses equivalent to decades in low-earth orbit, The data are consistent with the protons creating deep electron traps that increase the HEMT channel resistance. Postirradiation annealing at 300°C was able to restore ∼ 70% of the initial gm and IDS values in HEMTs receiving proton doses of 5 × 1010 cm-2.

Electric field and space-charge distribution in SI GaAs: effect of high-energy proton irradiation

The effect of irradiation on semi-insulating gallium arsenide Schottky diodes has been investigated by means of surface potential measurements and spectroscopic techniques. Before and after irradiation the electric field exhibits a Mott barrier-like distribution, and the box-shaped space charge modifies its distribution with irradiation. The increase in density or the generation of some traps changes the compensation ratio producing a deeper active region and a more homogeneous distribution of the electric field. The latter phenomenon is also observed by EBIC images of edge-mounted diodes.

The Effect of High-Energy Proton Irradiation on the Cardiovascular System of the Rhesus Monkey

There are no data available about the physiological response of mammals to total-body proton irradiation. Previous studies (1) have dealt with either the effects of focal irradiation or mortality after total-body irradiation. The present study was undertaken to compare the effects of total-body 'y-irradiation and proton irradiation on the cardiovascular system of the rhesus monkey. The effects of proton irradiation on blood pressure, heart rate, electrocardiogram, cardiac output, and the response to norepinephrine were studied at energies of 32, 55, 138, and 400 Mev. A single dose of about 3900 rads to the surface was used, since previous studies with y-rays (2) showed that this dose produced a pronounced fall in blood pressure, without signs of focal neurological damage and in the absence of significant fluid and electrolyte imbalance. Although differences in depth-dose distribution, particularly at low energies, preclude the calculation of a meaningful relative biological effectiveness (RBE) (3, 4), the data from the proton-irradiated animal are compared to data from y-irradiated animals. This comparison shows a similarity between the effect of total-body y-irradiation and proton irradiation at high proton energies and a dependence of the effects on depth-dose distribution at low proton energies.