Displacement Damage Dose Research Articles

Assessment of thermal and radiation induced creep in the dual cooled lead lithium blanket

The creep in recently designed blanket for the fusion nuclear science facility is described by decomposing it into thermal, irradiation and cavity swelling creep. Initial estimates of thermal creep using elastic high temperature rules showed that the recent heat transfer improvements at the first wall (FW) is feasible, and the FW can withstand heat flux of 0.35 MW/m2 at 3000 hrs without rupture. A viscoplastic model that is based on Norton's power law and relies on Multiphysics coupling of solid mechanics and heat transfer modules is used to capture the inelastic deformation in the blanket. Results showed that the design peak heat flux of 0.25 MW/m2 produced maximum thermal creep strain of 0.45 % and the relaxation of the thermal stress at the FW. Irradiation creep is prescribed to be proportional to the displacement damage dose and applied stress. The displacements from irradiation creep radially decrease from the FW to the back wall, but the maximum deformation is found at the back wall that is connected to the Helium manifold due to the high stresses at the region. Cavity swelling creep is dominant at steady state and combined with radiation creep to produce displacement of about 8 mm at the FW.

Application of displacement damage dose approach to low-energy proton irradiated GaInP/GaAs/Ge solar cells

In this paper, a displacement damage simulation model for proton-irradiated GaInP/GaAs/Ge triple junction (TJ) solar cells is constructed in Geant4, and the problem of the displacement damage dose curve deviation for low-energy protons is analyzed. The modeling results show that energy loss effects and local displacement damage are important factors for the deviation of the displacement damage dose curve. The non-ionizing energy loss (NIEL) values of GaAs sub-cells calculated by Geant4 can effectively improve the deviation of the curve caused by energy loss effects. The NIEL should be constrained by the structure and size of the device rather than just the proton energy and material type. In addition, the isotropic radiation field numerical method proposed in this paper allows the displacement damage simulation model constructed in Geant4 to be expediently applied to the radiation environment in space.

Study of displacement damage effects in InGaAs PIN photodiode under 10 MeV proton irradiation

The displacement damage effect of 10 MeV proton radiation on a high-speed InGaAs PIN photodiode has been experimentally investigated to evaluate the stability of the device in a space radiation environment. The results show that the dark current and low-frequency noise of the device increase significantly after irradiation, while the capacitance of the device decreases slightly after irradiation, where the spectral response parameters are less affected by irradiation. The increase in dark current is essentially linear with the displacement damage dose. Finally, the effect of proton irradiation on the optical communication system is simulated and the results show that the bit error rate of the system increases with the increase in irradiation fluence, which seriously affects the sensitivity of the optical communication system.

Degradation characteristics and equivalent analysis of InGaAsP space solar cells under proton and neutron irradiation

The effects of 2 MeV, 30 MeV proton and neutron irradiation on the performance of InGaAsP single junction solar cells were investigated. The degradation of electrical and optical properties was studied by experiment, such as I-V curve, external quantum efficiency, photoluminescence (PL) and scanning electron microscopy (SEM). Results show that the performance parameters of the solar cell degrade seriously with the increasing of the displacement damage dose. The PL results indicate that irradiation has a destructive effect on the photoelectric properties of materials. The carrier parameters were quantitatively calculated according to the PL normalized peak. The minority carrier lifetime attenuation model and equivalent displacement damage model were established to evaluate the on-orbit behavior of the InGaAsP solar cell.

Effect of ionizing radiation on quasi-floating gate transistors

Low power and low voltage are key in modern design. The quasi-floating gate (QFG) has proven to be an adequate choice in numerous applications. However, so far, its use has not spread in high-radiation environments because of the lack of studies on the performance of this technique under radiation. This work addresses the effect of ionizing radiation in the QFG transistor. To this end, a specific DUT has been designed and irradiated up to 2,25 Mrad. The experimental results show a tolerable reduction in the equivalent resistivity of the pseudoresistor (a reverse biased n-well PN junction). The effect is due to the increase in the reverse saturation current of the diode present between the pseudoresistor’s terminals, which is consistent with Displacement Damage Dose (DDD).

Degradation of vertical GaN diodes during proton and xenon-ion irradiation

We investigated the material stability of a vertical GaN Schottky barrier diode (SBD) against proton irradiations by making real-time measurements. The reverse current gradually decreased with increasing proton fluence. The current of the GaN SBD was reduced by 18% after proton irradiations with a displacement-damage dose (D d) of 1012 MeV g−1. We also examined signal and current degradation occurring in a vertical GaN-on-GaN p–n diode (PND) during xenon-ion irradiations. The signal gradually decreased with increasing xenon-ion fluence. Xenon-ion irradiations of D d = 1012 MeV g−1 reduced the collected charge in the PND by 11%. This signal degradation was close to the current degradation in the GaN SBD caused by the proton irradiations. We found that irradiations with D d > ∼1012 MeV g−1 degraded the performance of the GaN devices.

Study on Radiation Shielding of Inner Radiation Belt Protons

The radiation environment in the inner radiation belt is severe due to the large flux of high energy protons. Very few satellites are deployed in inner radiation belt today, and radiation shielding in this region did not get much attention. An imaging satellite developed by the Chinese Academy of Sciences will operate in the inner radiation belt in 2023. In order to shield the high energy protons, a new composite material was developed, and the shielding ability of this material was compared with that of Al, Ta, and sandwich materials by the Geant4 simulation tool. The results show that the new material can reduce the total ionizing dose by 40%, and the displacement damage dose by 50% compared with the Al shielding in same shielding mass. The number of transmitted protons under the shielding of Al and new materials was tested by using a 30 MeV~60 MeV proton beam on the ground, and the experimental results agree well with the simulation results.

Proton-Induced Displacement Damages in 2-D and Stacked CMOS SPADs: Study of Dark Count Rate Degradation

Dark count rate (DCR) degradation is measured on 40-nm 2D and stacked CMOS SPADs after proton irradiations. Mean DCR increase is plotted for different displacement damage doses (DDD) for two biasing conditions. Due to field enhancement effects such as Poole-Frenkel and phonon-assisted-tunneling, Non-Ionizing Energy Loss (NIEL) scaling is found to be dependent on the excess bias. Moreover, the associated damage factors are higher compared to pixels with unity gain photodiodes. A model predicting DCR increase with DDD based on field enhancement factor equations and damage energy deposited by the proton induced recoil spectrum is established and fits well with experimental data. Finally, activation energies are extracted: low values between 25 °C and 60 °C confirm the domination of field effects over thermal generation. Furthermore, large energy discrepancies seen at a fixed DCR increase are suggesting that defect structures could also have an impact on DCR distributions.

Design, Annealing, and Electric Field Effects on Proton and Gamma Irradiated MWIR HgCdTe Focal Plane Arrays

This work presents the performance degradation under irradiation of multi pixel-designs n/p mid-wavelength infrared HgCdTe focal plane arrays (FPA). Gamma and proton irradiations are conducted to single out the effects of total ionizing dose (TID) from the damage induced by displacement damage dose (DDD). The radiation-induced degradation is analysed through the current levels evolution and the random telegraph signal (RTS) phenomenon. TID damages the silicon read-out integrated circuit (ROIC), causing low current level and RTS pixels. The influence of photodiode size and electric field on TID-induced defects is investigated. The results suggest that leakage currents in the ROIC, induced by TID, are involved. DDD impacts the HgCdTe photodetection layer: the number of pixels with high dark current and RTS is increased in the FPA. The amount of DDD-induced degradation scales with the photodiode size and the applied bias. This suggests that the defects responsible for the evolution of the dark current and RTS are located in the HgCdTe depletion region. Annealing mechanisms of these effects indicate different types of DDD-induced defects.

Particle‐induced degradation of III–V multi‐junction solar cells under different configurations of displacement damage dose

AbstractThe solar arrays of spacecrafts are subjected to a severe radiative environment. Associated degradation rates are dependent on operational orbit configuration. The current approach used in models and tools to determine power degradation shall thus be validated to ensure good prediction accuracy. This paper reports on extensive irradiation test campaigns realized on triple‐junction solar cells to compare degradation induced by different configurations of irradiation reproducing nominally the same displacement damage dose (DDD) in the active layer. These test campaigns data are used to support the validation of a new tool developed to optimize prediction accuracy of solar cell degradation. The DDD equivalence between front/rear irradiation on solar cell assemblies and on bare solar cells, between different electron and proton energies, as well as the verification of the superposition principle are addressed. Results are conclusive regarding the equivalence of degradation obtained with electrons, protons and/or combined electrons and protons, accounting for local shielding.

Electrical deterioration of 4H-SiC MOS capacitors due to bulk and interface traps induced by proton irradiation

In this study, the displacement damage dose (DDD) effects of proton irradiation on bulk crystal and interfacial properties of 4H-SiC MOS capacitors (MOSCs) were investigated. The Monte Carlo calculation code named SRIM (Stopping and Range of Ions in Matter) was first used to predict the depth profiles and damage distributions of protons. The 4H-SiC MOSCs were irradiated with 60, 100, 150 keV protons to fluences ranging from 5 × 1011 to 5 × 1013 cm−2. Capacitance-voltage (C-V) curves of the MOSCs were then measured to characterize the variation of the electrically active defects in 4H-SiC MOSCs. The results revealed that the non-ionization energy loss of incident protons leads to the accumulation of the primary defects in bulk SiC crystal as well as the increase of the interface traps between SiO2 and SiC crystal. A distinctive bump phenomenon was found in the weak inversion region of the C-V curve and it became more prominent with the increase of proton fluence, providing evidence for the existence of bulk traps. Furthermore, the incident proton energy is also a crucial factor in interface deterioration, suggesting that more interface traps would be formed when the proton damage peak is closer to the SiO2/SiC interface.

Development of a method for calculating effective displacement damage doses in semiconductors and applications to space field.

The displacement damage dose (DDD) is a common index used to predict the life of semiconductor devices employed in space-based environments where they will be exposed to radiation. The DDD is commonly estimated from the non-ionizing energy loss based on the Norgett-Robinson-Torrens (NRT) model, although a new definition for a so-called effective DDD considers the molecular dynamic (MD) simulation with the amorphization in semiconductors. The present work developed a new model for calculating the conventional and effective DDD values for silicon carbide (SiC), indium arsenide (InAs), gallium arsenide (GaAs) and gallium nitride (GaN) semiconductors. This model was obtained by extending the displacement per atom tally implemented in the particle and heavy ion transport code system (PHITS). This new approach suggests that the effective DDD is higher than the conventional DDD for arsenic-based compounds due to the amorphization resulting from direct impacts, while this relationship is reversed for SiC because of recombination defects. In the case of SiC and GaN exposed to protons, the effective DDD/conventional DDD ratio decreases with proton energy. In contrast, for InAs and GaAs, this ratio increases to greater than 1 at proton energies up to 100 MeV and plateaus because the defect production efficiency, which is the ratio of the number of stable displacements at the end of collision cascade simulated by MD simulations to the number of defects calculated by NRT model, does not increase at damage energy values above 20 keV. The practical application of this model was demonstrated by calculating the effective DDD values for semiconductors sandwiched between a thin glass cover and an aluminum plate in a low-Earth orbit. The results indicated that the effective DDD could be dramatically reduced by increasing the glass cover thickness to 200 μm, thus confirming the importance of shielding semiconductor devices used in space. This improved PHITS technique is expected to assist in the design of semiconductors by allowing the effective DDD values for various semiconductors having complex geometries to be predicted in cosmic ray environments.

A Possibility for Large-Scale Production of 238Pu in Light-Water Reactor VVER-1000

This paper considers the possibility for large-scale production of plutonium isotope 238Pu in the light-water nuclear power reactor VVER-1000. 238Pu is a unique source of long-term autonomous energy supply in various devices for remote regions of the Earth and in outer space. The design of the irradiation device with 237NpO2 as a starting material is proposed, which is placed in the central zone of the VVER-1000 reactor core and makes it possible to achieve 8% of the specific Pu production (Pu/237Np) by optimizing the pitch of NpO2-rod lattice. The computations showed that the scale of 238Pu production in the irradiation device was remarkably larger (2 ÷ 7 times more) than similar values in research reactors. At the same time, the use of heavy neutron moderators with low neutron absorption (natural lead or lead isotope 208Pb) around the NpO2 fuel assembly (FA) made it possible to obtain high-purity 238Pu with the content of 236Pu below 2 ppm. The paper also shows that if the irradiation device is placed in central zone of the VVER-1000 reactor core, then the displacement damage dose in the reactor vessel remains low enough to conserve its strength properties throughout the entire period of the reactor operation (60 years).

Research on the Synergistic Effect of Total Ionization and Displacement Dose in GaN HEMT Using Neutron and Gamma-Ray Irradiation.

This paper studies the synergistic effect of total ionizing dose (TID) and displacement damage dose (DDD) in enhancement-mode GaN high electron mobility transistor (HEMT) based on the p-GaN gate and cascode structure using neutron and 60Co gamma-ray irradiation. The results show that when the accumulated gamma-ray doses are up to 800k rad(Si), the leakage-current degradations of the two types of GaN HEMTs with 14 MeV neutron irradiation of 1.3 × 1012 n/cm2 and 3 × 1012 n/cm2 exhibit a lower degradation than the sum of the two separated effects. However, the threshold voltage shifts of the cascode structure GaN HEMT show a higher degradation when exposed to both TID and DDD effects. Moreover, the failure mechanisms of the synergistic effect in GaN HEMT are investigated using the scanning electron microscopy technique. It is shown that for the p-GaNHEMT, the increase in channel resistance and the degradation of two-dimensional electron gas mobility caused by neutron irradiation suppresses the increase in the TID leakage current. For the cascode structure HEMT, the neutron radiation-generated defects in the oxide layer of the metal–oxide–semiconductor field-effect transistor might capture holes induced by gamma-ray irradiation, resulting in a further increase in the number of trapped charges in the oxide layer.

Effect of helium and its synergism with displacement damage on microstructure of CLAM steel investigated by single, sequential and simultaneous Fe and He ion irradiations

The reduced-activation ferritic/martensitic steel, China Low-Activation Martensitic (CLAM) steel, was irradiated with single Fe, sequential He/Fe, sequential Fe/He, and simultaneous Fe+He ion beam irradiations at 350 ℃–550 ℃ to a peak displacement damage dose of 15 dpa with 0 - 110 appm/dpa He to explore the effect of He and its synergism with displacement damage on microstructure evolution. The microstructures of all the irradiated specimens were investigated by transmission electron microscope (TEM). For Fe/He sequential irradiation, He inhibited the growth of dislocation loop induced by high-temperature He post-irradiation and reduced the number density of loops. Non-spherical He bubbles were observed only at post-injection He at 550 °C. The size of non-spherical He bubbles produced at 110 appm/dpa was about twice as large as 11 appm/dpa, and the number density increased about 6.4 times. The number density of dislocation loops induced by sequential He/Fe irradiation is the highest, and the average size of loops is comparable to that caused by simultaneous Fe+He irradiation. Moreover, the sequential Fe/He irradiation induced the lowest number density of loops of approximately 64% of the simultaneous Fe+He irradiation. The spherical bubble was observed in all irradiation with He injection above 350 ℃. The average size of spherical He bubbles induced by simultaneous Fe+He irradiation is the largest, and the number density is about 2.6 times that of the sequential Fe/He irradiation. The synergisms of He in different irradiation sequences were analyzed systematically, which helps to better understand the evolutionary processes of the synergistic effect of He and displacement damage.

Displacement Damage Effects in Backside Illuminated CMOS Image Sensors

Displacement damage effects in backside illuminated CMOS image sensors (BSI CISs) are investigated. Several BSI CISs with distinct epitaxial layer thicknesses are irradiated by several protons and neutrons to study the influence of technology parameters and radiation parameters on the radiation response of these imagers. A significant degradation in quantum efficiency (QE) is observed for thick epitaxial layer at the absorbed dose of 1230 TeV/g. Dark-current damage factor of 0.141 e⁻·s⁻¹·μ m⁻³·(TeV/g)⁻¹ is determined in BSI CIS. The influence of particle types, particle energy, and radiation fluence on dark current distributions is presented at the same displacement damage dose (DDD). Dark current random telegraph signal (DC-RTS) is reported and the variation in epitaxial layer thickness has no influence on DC-RTS behavior. This work highlights the relationship between key parameters and DDD: the limiting factors of the imager performance are single pixel [hot pixel and random telegraph signal (RTS) pixel] at a low DDD range, mean dark current and single pixel at a medium DDD range, and mean dark current in the high DDD case, respectively.

Countdown to perovskite space launch: Guidelines to performing relevant radiation-hardness experiments

<h2>Summary</h2> Perovskite photovoltaics (PVs) are under intensive development for promise in terrestrial energy production. Soon, the community will find out how much of that promise may become reality. Perovskites also open new opportunities for lower cost space power. However, radiation tolerance of space environments requires appropriate analysis of relevant devices irradiated under representative radiation conditions. We present guidelines designed to rigorously test the radiation tolerance of perovskite PVs. We review radiation conditions in common orbits, calculate nonionizing and ionizing energy losses (NIEL and IEL) for perovskites, and prioritize proton radiation for effective nuclear interactions. Low-energy protons (0.05–0.15 MeV) create a representative uniform damage profile, whereas higher energy protons (commonly used in ground-based evaluation) require significantly higher fluence to accumulate the equivalent displacement damage dose due to lower scattering probability. Furthermore, high-energy protons may "heal" devices through increased electronic ionization. These procedural guidelines differ from those used to test conventional semiconductors.

Radiation Hardness Study of Single-Photon Avalanche Diode for Space and High Energy Physics Applications.

The radiation hardness of 180 nm complementary metal–oxide–semiconductor (CMOS) and 55 nm bipolar–CMOS–double-diffused MOS single-photon avalanche diodes (SPADs) is studied using 10 MeV and 100 MeV protons up to a displacement damage dose of 1 PeV/g. It is found that the dark count rate (DCR) levels are dependent on the number and the type of defects created. A new stepwise increase in the DCR is presented. Afterpulsing was found to be a significant contributor to the observed DCR increase. A new model for DCR increase prediction is proposed considering afterpulsing. Most of the samples under test retain reasonable DCR levels after irradiation, showing high tolerance to ionizing and displacement damage caused by protons. Following irradiation, self-healing was observed at room temperature. Furthermore, high-temperature annealing shows potential for accelerating recovery. Overall, the results show the suitability of SPADs as optical detectors for long-term space missions or as detectors for high-energy particles.

Displacement damage dose analysis of the output characteristics of In0.5Ga0.5P and Cu(In,Ga)(S,Se)2 solar cells irradiated with alpha ray simulated helium ions

To investigate the applicability of radiation-hard indium–gallium–phosphide (InGaP) and copper–indium–gallium–sulfide–selenide (CIGS) solar cells to dosimeter devices without any modification, we irradiated high-energy He+ ions, which were simulated α-ray particles, to an InGaP and a CIGS solar cell. We found that both types of solar cells have sufficient resistance to He+ ions. By using displacement damage dose (DDD) analysis, the obtained He+ ion-induced degradation trends were compared with those induced by high-energy electrons and protons, and we found that the degradation trends due to He+-ions, electrons, and protons aligned on the same curve when we plotted the data as a function of a modified DDD conversion equation, which originally was applied to space solar cells. The obtained DDD formulas enable us to predict the device lifetime or correction of an output signal for degradation when such solar cells are employed as a dosimeter.

Displacement damage effects in proton irradiated vertical-cavity surface-emitting lasers

The displacement damage effects of vertical-cavity surface-emitting lasers (VCSELs) irradiated by 3 and 10 MeV protons in the range of Ф = 6.7 × 1012 p cm−2 to Ф = 1.6 × 1014 p cm−2 were investigated. The threshold current exhibited consistent degradation at the same displacement damage dose, as did the series resistance. Additionally, the external quantum efficiencies of 850 and 680 nm VCSELs were degraded by 2% and 21%, respectively. Further, the threshold current of the 850 nm VCSEL was restored by 14% after annealing at 20 mA, which is remarkably higher than that achieved by annealing only at high temperatures. These results support the applicability of VCSELs to both data communication and instrumentation applications in harsh radiation environments.