Radiation-induced Displacement Damage Research Articles

Electrical characterization and temperature reliability of 4H-SiC Schottky barrier diodes after Electron radiation

In this study, the operation of commercial SBD-based on 4H-SiC after radiation was assessed. The devices were subjected to electron radiation with an energy of 1.7 MeV at different fluences. Then the electrical characteristics of the devices were measured, and related parameters were calculated. The results show that the devices display good radiation resistance at the high fluence of 1015 e/cm2. However, the performance of the devices degrade when the total fluence is 1 × 1016 e/cm2. The variable temperature test and deep-level transient spectrum (DLTS) tests reveal the cause of performance degradation under high fluence. The variable temperature test result shows that the ideality factor of the device at 1 × 1016 e/cm2 increases compared with that devices, indicating more recombination centers are introduced. The donor concentration (ND) significantly decreases at 1 × 1016 e/cm2, and increases with increasing temperature in the range of 350–450 K. The DLTS results show that the change of ND with temperature is related to the decrease of Ec-0.91 defect concentration. During the variable temperature test, certain changes are found in the defects and the defects are due to the repair of the ionization damage during the heating process, the degeneration of the electrical characteristics is mainly caused by the ionization damage rather than the displacement damage. Finally, the radiation-induced displacement damage is mainly located in the region near the metal-semiconductor interface.

Improved methods for calculating electron, positron, and photon radiation-induced displacement damage cross sections

Radiation damage is a key challenge for materials. Accurate evaluation of radiation damage is a starting point for investigating the behaviors of materials used in a radiation environment. The present work proposes improved methods for calculating the primary radiation damage cross sections induced by light particles, including electrons, positrons, and photons. The main improvements compared with previous methods are: (1) accurate Mott cross section rather than the McKinley-Feshbach analytical approach is used for electron and positron scattering; (2) data and methods recommended by the International Commission on Radiation Unit and measurements (ICRU) are systematically applied for computing the stopping powers of electron and positron; (3) accurate differential cross section by combining different models instead of some simple approaches is used for pair production. The electron, positron, and photon irradiation-induced displacement cross sections for various important elements covering a large range of atomic numbers (from Li to U) are computed with the improved methods for energy up to 100 MeV. The calculated displacement cross sections are also tabulated so that they can be simply used for further applications.

Comprehensive approach to determination of space proton-induced displacement defects in silica optical fiber

Silica-based optical fibers presents a variety of applications used in radiation environments such as space, fusion facilities, accelerators and nuclear power plants. The radiation-induced displacement damage in optical fibers resulting in point defects may lead to attenuation signals that is a major concern for these applications. The present study proposes a computational approach to the calculation of the proton-induced displacement damage in vitreous silica. Therefore, Geant4 as a Monte Carlo particle transport code has been used to obtain the knock-on atom distributions caused by the interaction of space trapped proton with vitreous silica during an ISS mission. Moreover, molecular dynamics simulations using ReaxFF potential have been performed to produce the initial vitreous silica structure to evaluate the displacement damage cascades by LAMMPS package. The results show that ReaxFF has an appropriate potential to produce and evaluate the vitreous silica structure that provides better agreement with experimental data at both short-range and medium-range order. Furthermore, ODC(Si3) and NBOHC(O1) are dominant defect species created in the vitreous silica after trapped proton irradiation, where the total number of defects have increased on average by 94 for each keV increasing in PKA energy approximately.

Effect of Hydrogen on Radiation-Induced Displacement Damage in AlGaN/GaN HEMTs

To explore the role of hydrogen in radiation degradation of AlGaN/GaN high-electron-mobility transistors (HEMTs), the performance degradation of the hydrogen untreated and pretreated devices is compared under the exposure of carbon ions. The energy of carbon ions is chosen as 7.6 MeV, and the maximum fluence reaches 4 ×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> . By electrical character measuring, it is found that the positive shift of the threshold voltage and the decrease of the transconductance occur after to the irradiation. Hydrogen pretreatment accelerates the shift of threshold voltage and the decrease of the transconductance. The threshold voltage of the device is almost unchanged under 1-MeV electron irradiations. This means that the displacement damage leads to the shift of the threshold voltage. The height of Schottky barrier hardly changes in the hydrogen pretreated devices, showing that the ionization defects such as the formation of interface states under the gate are not the main cause of device degradation. Deep level transient spectrum (DLTS) results show that the irradiations cause the increase of gallium vacancies, and the hydrogen pretreatment inhibits its formation. According to the first principle calculation, the existence of hydrogen in GaN layer can reduce the formation energy of and the number of charges of the defects. It is speculated that hydrogen atoms participate in the evolution of radiation defects, which changes the types and number of defects in the devices.

Displacement Damage Effects Mitigation Approach for Heterojunction Bipolar Transistor Frequency Synthesizers

This work focuses on the design issues of radio frequency (RF) bipolar integrated circuits (ICs) as a part of frequency synthesizers for extreme environmental applications. It is shown that silicon–germanium (SiGe) and gallium arsenide (GaAs) heterojunction bipolar transistors (HBTs) as well as bipolar RF ICs (including frequency dividers, voltage-controlled oscillators, and wide-band amplifiers) are highly sensitive to ambient temperature and radiation-induced displacement damage. This article also presents a design approach based on specialized HBT macromodels and hardening techniques.

A study on triple-junction GaInP2/InGaAs/Ge space grade solar cells irradiated by 24.5 MeV high-energy protons

This paper was reported high-energy proton exposure effects on triple-junction GaInP2/InGaAs/Ge space grade solar cells. In order to explore the degradation of solar cells in hard radiation environments detailed and systematic analysis were performed, and the results were presented. The irradiation process was carried out using 24.5 MeV protons with doses ranging from 0 to 170 Gy. The degradation of output parameters of solar cells was studied as a function of damaged dose using light current–voltage measurements. The current–voltage characteristics indicated that the short circuit current was degraded less than the open circuit voltage because the base sub-cell of GaAs was significantly damaged. To analyze the effects of radiation-induced displacement damage on cell performance SRIM simulation was performed. Capacitance and conductance measurements were done to knowledge about the carrier concentration and interface trap density. A decrease in carrier concentration and a small increase in interface trap density were observed.

Progress of radiation effects of silicon photonics devices

Silicon photonics is a fundamental technology, which has great potential applications in optical interconnection for telecom, datacom, and high performance computers, as well as in bio-photonics. Currently considered are the photonics integrated circuits that are able to work in harsh environments such as high energy equipment and future space systems including satellites, space stations and spacecraft. The understanding of the radiation effects of the photonics devices is critical for fabricating radiation hardened photonic integrate chips and maintaining the performance of the devices and the systems. In this paper, the recent progress of the radiation effects of silicon photonic components is summarized. The effects of the high energy particles that possibly degrade the performance of the device are explained, and the response of the passive and active device under radiation are reviewed comprehensively, including waveguides, ring resonators, modulators, detectors, lasers and optical fibers and so on. For passive devices, radiation-induced effects include accelerated-oxidation of the structures, radiation-generated lattice defects, and amorphous densification or compaction in the optical materials. The effective refractive index of the passive device may change consequently, leading the working frequency to shift, the optical confinement to decrease, and the optical power to leak, which accounts for the extra loss or other performance degradation behaviors. For photodetectors and lasers, radiation-induced displacement damage will be dominant. The induced point defects localized in the silicon layer bring about deep level in the forbidden band, acting as generation-recombination centers or trap centers of tunneling effect, which will compensate for either donor or acceptor levels, degrading the response of these optoelectronic device significantly. The plasma dispersion effect is the mainstream approach to building the silicon electro-optic modulators, which will suffer ionization damage in the high energy particle environment, because the interface-trapped hole caused by ionizing radiation reduces the carrier concentration in the depletion region and even induces the pinch-off of the p-doped side of the modulator, which may result in device failure. To improve the radiation hardness of the silicon photonic device, the passivation of the surface, optimization of the waveguide shape, and the choice of appropriate thickness of the buried oxide layer are possible solutions, and more effective approaches are still to be developed.

Modeling charge collection efficiency degradation in partially depleted GaAs photodiodes using the 1- and 2-carrier Hecht equations

The Hecht equation can be used to model the nonlinear degradation of charge collection efficiency (CCE) in response to radiation-induced displacement damage in both fully and partially depleted GaAs photodiodes. CCE degradation is measured for laser-generated photocurrent as a function of fluence and bias in Al0.3Ga0.7As/GaAs/Al0.25Ga0.75As p-i-n photodiodes which have been irradiated with 12MeVC and 7.5MeV Si ions. CCE is observed to degrade more rapidly with fluence in partially depleted photodiodes than in fully depleted photodiodes. When the intrinsic GaAs layer is fully depleted, the 2-carrier Hecht equation describes CCE degradation as photogenerated electrons and holes recombine at defect sites created by radiation damage in the depletion region. If the GaAs layer is partially depleted, CCE degradation is more appropriately modeled as the sum of the 2-carrier Hecht equation applied to electrons and holes generated within the depletion region and the 1-carrier Hecht equation applied to minority carriers that diffuse from the field-free (non-depleted) region into the depletion region. Enhanced CCE degradation is attributed to holes that recombine within the field-free region of the partially depleted intrinsic GaAs layer before they can diffuse into the depletion region.

Increased Radiation Hardness of Short-Channel Electron-Irradiated Si1-xGex Source/Drain p-Type Metal Oxide Semiconductor Field-Effect Transistors at Higher Ge Content

In this work, it is shown that the maximum hole mobility of compressively strained Si1-xGex source–drain (S/D) p-MOSFETs is degraded after high-fluence 2 MeV electron irradiation, suggesting the loss of strain in the Si channel caused by the radiation-induced displacement damage. This is supported by the fact that the mobility reduction after irradiation is larger for SiGe S/D devices than for Si references at the same fluence (5×1017 cm-2) and becomes more pronounced for shorter gate lengths. At the same time, however, it is found that the extent of mobility reduction becomes smaller for p-MOSFETs with a higher Ge content (35%, compared with 20 or 30%). Finally, it is concluded that, for shorter devices, the displacement-damage-related degradation mechanism becomes less pronounced with increasing Ge content in Si1-xGex S/D regions.

Displacement Damage Effects in Irradiated Semiconductor Devices

A review of radiation-induced displacement damage effects in semiconductor devices is presented, with emphasis placed on silicon technology. The history of displacement damage studies is summarized, and damage production mechanisms are discussed. Properties of defect clusters and isolated defects are addressed. Displacement damage effects in materials and devices are considered, including effects produced in silicon particle detectors, visible imaging arrays, and solar cells. Additional topics examined include NIEL scaling, carrier concentration changes, random telegraph signals, radiation hardness assurance, and simulation methods for displacement damage. Areas needing further study are noted.

Characterization of Bulk Damage in CMOS MAPS With Deep N-Well Collecting Electrode

Monolithic active pixel sensors in CMOS technology, featuring a deep N-well as the collecting electrode (so called DNW MAPS), have been exposed to neutrons from a nuclear reactor, up to a total 1 MeV neutron equivalent fluence of about $3.7\times 10^{13}~{\hbox {cm}}^{-2}$ . The irradiation campaign was aimed at studying the effects of radiation induced displacement damage on the charge collection properties of the device, which was conceived for applications to charged particle tracking in high energy physics experiments. A number of different techniques, including electrical characterization of the front-end electronics and of DNW diodes, laser stimulation of the sensors and tests with $^{55}{\hbox {Fe}}$ and $^{90}{\hbox {Sr}}$ radioactive sources, has been employed for evaluating the device operation before and after irradiation. This paper discusses the measurement results and their relation with the bulk damage mechanisms underlying performance degradation in DNW MAPS.

Phosphors as Sensors for Radiation-Induced Displacement Damage

AbstractThe radiation-induced displacement damage in yttrium borate (YBO3) is studied under X-ray, proton, and alpha irradiation. The photoluminescence (PL) was tested before and after irradiation to determine whether damage occurred and whether it could be queried by examining the PL spectrum. Two different dopants (cerium and europium) were used to activate the phosphor because each provides not only a different spectral signature but also a different mechanism for altering the spectrum between the pre- and post-PL measurements. X-rays, being primarily ionizing radiation, did not show any significant change between the pre and post measurements. We expected protons and alphas to damage the crystal structure, evidence of which could be seen in the change in the spectra before and after irradiation. However, we found no change under alpha exposure (3.6 × 1010 particles/cm2) and a significant change after proton exposure (5 × 1015 particles/cm2). While the material appears to be sensitive to protons, we cannot rule out its sensitivity to alphas because the alpha fluence may be too low to show an effect. This result provides strong indication that our materials are being damaged by particle radiation and that the radiation effects can be quantified.

Impact of Alpha Particles on the Electrical Characteristics of TiO$_{2}$ Memristors

Titanium-oxide (TiO2 ) memristors exposed to 1-MeV alpha particles exhibit only minor changes in the electrical response for ion fluencies up to 1014 cm - 2. At higher fluence levels, virgin and off-state devices exhibit measurable increases in current conduction between the two platinum (Pt) electrodes. Analysis, supported by radiation transport and numerical device simulations, suggests that radiation-induced displacement damage in the TiO2 film increases the density of oxygen vacancies, thereby altering both resistivity in the bulk of the transition-metal oxide and the junction characteristics of Pt-TiO2 interface. Nevertheless, the experimental results indicate continued switching functionality of the memristors even after exposure to 1015 cm- 2 alpha particles. The high intrinsic vacancy density in the devices prior to radiation exposure is identified as the primary feature contributing to apparent radiation hardness.

Focal plane damage analysis by the space radiation environment in Aura satellite orbit

Radiation-induced displacement damage, which has caused the increase of the dark current in the focal plane adopted in the Ozone Monitoring Instrument (OMI), was studied in regards of the primary protons and the secondaries generated by the protons in the orbit. Using the Monte Carlo N-Particle Transport Code System (MCNPX) version 2.4.0 along with the Stopping and Range of Ions in Matter version 2010 (SRIM2010), effects of the primary protons as well as secondary particles, including neutron, electron, and photon were investigated. After their doses and fluxes that reached onto the charge-coupled device (CCD) were examined, displacement damage induced by major sources was presented.

Impact of the displacement damage in channel and source/drain regions on the DC characteristics degradation in deep-submicron MOSFETs after heavy ion irradiation

This paper mainly reports the permanent impact of displacement damage induced by heavy-ion strikes on the deep-submicron MOSFETs. Upon the heavy ion track through the device, it can lead to displacement damage, including the vacancies and the interstitials. As the featured size of device scales down, the damage can change the dopant distribution in the channel and source/drain regions through the generation of radiation-induced defects and thus have significant impacts on their electrical characteristics. The measured results show that the radiation-induced damage can cause DC characteristics degradations including the threshold voltage, subthreshold swing, saturation drain current, transconductance, etc. The radiation-induced displacement damage may become the dominant issue while it was the secondary concern for the traditional devices after the heavy ion irradiation. The samples are also irradiated by Co-60 gamma ray for comparison with the heavy ion irradiation results. Corresponding explanations and analysis are discussed.

Atomic-Scale Mechanisms for Low-NIEL Dopant-Type Dependent Damage in Si

While calculated non-ionizing energy loss (NIEL) generally correlates well to first order with radiation-induced displacement damage rates, it does not account for some well-known differences in damage rates for n- and p-type Si. Here we show that the magnitude of these differences, DeltaKn-p, correlates closely with the fraction of total displacement damage due to low-energy primary knock-on atom (PKA) recoils. The primary products of these displacement damage events, with PKA recoils <~ 2 keV, are close vacancy-interstitial pairs, or Frenkel Pairs (FPs). Based on previous studies of vacancy-dopant complex stabilities in Si, and new parameter-free quantum mechanical calculations of FP properties, details of the stable defect profiles arising from low-energy PKA recoil events are shown to give rise to non-zero values of DeltaKn-p

Review of displacement damage effects in silicon devices

This paper provides a historical review of the literature on the effects of radiation-induced displacement damage in semiconductor materials and devices. Emphasis is placed on effects in technologically important bulk silicon and silicon devices. The primary goals are to provide a guide to displacement damage literature, to offer critical comments regarding that literature in an attempt to identify key findings, to describe how the understanding of displacement damage mechanisms and effects has evolved, and to note current trends. Selected tutorial elements are included as an aid to presenting the review information more clearly and to provide a frame of reference for the terminology used. The primary approach employed is to present information qualitatively while leaving quantitative details to the cited references. A bibliography of key displacement-damage information sources is also provided.

Radiation-induced displacement damage in silicon carbide blue light-emitting diodes

The effect of electron irradiation on the minority carrier lifetime of silicon carbide (SiC) light-emitting diodes has been evaluated. It is shown that the frequency-domain lifetime measuring technique used on GaAs LEDs (light emitting diodes) can be used successfully on SiC devices to determine a unique value for damage constant at energies not too close to threshold. Although the electron threshold energy for displacement damage is lower than that for GaAs by a factor of 2.5 because of the smaller mass of the carbon atom, at energies above 0.5 MeV the damage constant for SiC is more than three orders of magnitude lower than for GaAs, indicating greatly superior performance in most radiation environments. Preliminary annealing studies indicate significantly different recovery behavior for damage by electrons of different energies.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Radiation damage in non-fissile metallic alloys

A general survey is presented of radiation-induced displacement damage in non-fissile metallic alloys. The importance of the spatial arrangement of the vacancies and interstitials so produced is highlighted, especially as a guide to formulating an appropriate gauge for the various radiation-induced phenomena considered—i.e. hardening, embrittlement, growth, creep, swelling and fracture. The present level of theoretical understanding and the technological import of these phenomena are also assessed.

The effects of radiation-induced displacement damage on impurity conduction in gallium arsenide

The effects of 60Co γ-ray and high-energy neutron displacement damage on impurity conduction in epitaxial gallium arsenide were investigated. The activation energy (ε2) associated with the transition regime of the impurity conduction process was found to increase by a factor of 5 as a result of 60Co γ irradiation, and only by a factor of 1.6 for a comparable neutron irradiation. In addition, the ratio of the Hall carrier density at low and high temperatures, (nH)4 K/(nH)300 K, decreased by a larger amount for 60Co γ irradiation than for neutron irradiation. The effects of neutron irradiation are explained in terms of increased compensation. For the case of 60Co γ irradiation, it is postulated that a new donor level is introduced which does not participate in the impurity conduction process. In addition, with respect to the impurity conduction process, it is found that ε2 is proportional to ε1 (the conduction-band activation energy) and varies inversely with neutral donor spacing in accord with the model proposed by Mikoshiba. Also ρ30, the hopping regime resistivity, is found to vary inversely with the square of the free-carrier concentration and exponentially with the quantity 0.6/ND1/3a.