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The X-ray free-electron laser (XFEL) at the Pohang Accelerator Laboratory (PAL), Pohang, South Korea, provides X-ray energies of up to 15 keV depending on the experimental purpose. Silicon-based devices have been used as diagnostic devices and detectors for X-rays in experimental stations. Considering recent domestic and international circumstances, developing silicon-based detectors in-house is necessary. We developed a silicon p-intrinsic-n (PIN) photodiode (PD) for X-ray detection, and its performance was investigated and compared with that of a commercial PD used in the PAL-XFEL. The PD was designed to be 1 cm $\times1$ cm in size, and it used the junction side for signal readout and the ohmic side for X-ray entrance. Considering the absorption length of 12-keV X-rays suitable for crystallography, a 500- $ {\mu }\text{m}$ -thick silicon wafer with a high resistivity was used for PD fabrication. It has a guard ring, an n+ edge field shaper, and an antireflection coating (ARC) and is available in four different types based on the metal structure of the junction and ohmic sides. We present here the electrical characteristics of the PDs. The depletion voltage at which the bulk of the PD is fully depleted was determined to be 119.7 ± 8.2 V from bulk capacitance measurements, and the operation voltage of the PD was set to 200 V. PDs with leakage currents less than 30 nA/cm2 at the operation voltage were chosen for performance measurements. The signal-to-noise ratio (SNR) with a Sr-90 radioactive source corresponding to the minimum ionizing particle (MIP) and the quantum efficiency (QE) for wavelengths of 300–1000 nm were measured. Beam tests were conducted at the PAL-XFEL using 600-, 900-, and 1200-eV X-rays where the responses to ultrahigh brightness and ultrashort X-ray pulses were checked. The energy resolutions were measured using gamma-ray radioactive sources, Am-241 (59.5 keV), and Ba-133 (31.0 and 81.0 keV). The differences in performance among the PD types are presented herein in terms of the electrical characteristics, SNR, QE, response to X-ray pulses, and energy resolutions. The results of the fabricated PDs were also compared with those of a commercial PD. [ABSTRACT FROM AUTHOR]

Neutron displacement effects in LM158L and LM158V bipolar amplifiers with lateral p-n-p (LPNP) and substrate p-n-p (SPNP) input transistors, respectively, were investigated based on neutron irradiation experiments and TCAD simulation. Experimental results suggest that the type of input transistor of the amplifier has great impact on the neutron displacement degradation. The input bias current and input offset current of the amplifier with SPNP input transistor increase more than that with LPNP input transistor, and more severe degradation in SPNP than that in LPNP leads to the corresponding more severe degradation in the specific amplifier. TCAD simulations were performed to analyze the physical mechanism of neutron displacement effects in these two kinds of input transistors. For LPNP, the hole current is much closer to the surface of the silicon, however for SPNP, the hole current is much deeper into the bulk silicon, so the displacement traps in whole bulk all contribute to the total recombination. Therefore, the total recombination in SPNP is larger than that in LPNP, resulting in more severe degradation under neutron irradiation. [ABSTRACT FROM AUTHOR]

The effect of super-cadmium neutron-induced defects on radiation detection performance of Schottky barrier diodes, fabricated on 250- $\mu \text{m}$ -thick 4H-SiC epitaxial layers with ultralow intrinsic defect concentration, has been studied. The epilayers were irradiated in a TRIGA Mark II nuclear reactor dry instrumentation tube [intrareflector irradiation system or (IRIS)] in the net neutron fluence range 1010–1013 cm−2. Current–voltage (I–V) and capacitance–voltage (C–V) characteristics revealed that the detectors irradiated up to a fluence of 1012 cm−2 maintained a Schottky diode behavior. Radiation detection measurements showed an energy resolution of 28 keV (0.5%) full-width at half-maximum (FWHM) when exposed to 5486-keV alpha particles for the epilayers irradiated up to a neutron fluence of 1011 cm−2, which broadened to 42 keV (0.8%) FWHM for a fluence of 1012 cm−2. I–V and C–V measurements revealed substantial donor compensation in the epilayer irradiated at a fluence of ~1013 cm−2; however, the detector still worked satisfactorily with an energy resolution of 76-keV (1.8%) FWHM. The degradation in the detector performance with increased neutron dose was attributed to the trapping of charge carriers in the radiation-induced trap centers. Deep-level transient spectroscopy studies in the detector irradiated with a fluence of 1010 cm−2 revealed the formation of EH5 centers along with an unidentified deep electron trap located at 1.8 eV below the conduction band edge, both usually absent in as-grown 250- $\mu \text{m}$ 4H-SiC epilayers. A drift-diffusion model of charge transport showed a degradation in hole diffusion length from 10 $\mu \text{m}$ at a neutron fluence of 1010 cm−2 to $2.6~\mu \text{m}$ at 1012 cm−2 indicating formation of hole-trap centers as well. [ABSTRACT FROM AUTHOR]

Ionizing radiation experiments on gated controlled lateral p-n-p (GLPNP) bipolar transistor show that the base current obtained by gate sweeping (GS) exhibits two “unusual” phenomena, including decreasing in amplitude and narrowing in peak profile after radiation. Both interface traps and border taps are called switching states due to their similar recombination effects on substrate carriers. The two traps can attribute to the base current. The separation of interface traps and border taps is achieved by a frequency-dependent charge pumping technique. Based on Technology Computer-Aided Design (TCAD) simulation in conjunction with device theory, this work suggests that the two “unusual” phenomena can be explained by the combined effects of border traps and interface traps. [ABSTRACT FROM AUTHOR]

The response of floating gate (FG) devices to 60Co $\gamma $ -rays under switched bias conditions is studied by real-time monitoring of the threshold voltage evolution with accumulated dose. Samples were fabricated in a 1.5- $\mu \text{m}$ CMOS process, suitable for dosimetry applications. A physics-based numerical model of total ionizing dose (TID) effects in FG MOS devices is developed, taking into consideration the dominant microscopic processes leading to charge accumulation/neutralization across the structure. The main parameters of the model are the capture and neutralization rates in both oxides (tunnel and interpoly), and the initial FG charge. A dataset of experimental measurements is used to extract those parameters. Then, the model is applied to predict the response of later experiments. In one case, the device is irradiated under different switching bias voltages, yielding a mean absolute error of 1.8%. With the same set of parameters, but using another device, the model is able to predict with an error of 2.1%, an exposition performed with a $V_{t}$ -shift range twice the one in the first experiment. The predictive power of the model in a wide range of experimental conditions relies on the physics principles behind it. Combined experiments plus simulations allow to distinguish how charges in each layer of the structure evolve and contribute to the overall response. As an application of the model, cycled measurement technique for dosimetry is investigated. [ABSTRACT FROM AUTHOR]

In this work, the thermally stimulated current (TSC) technique has been used to investigate the properties of the radiation-induced interstitial boron and interstitial oxygen defect complex by 23-GeV ($E_{\text {kin}}$) protons, including activation energy, defect concentration, as well as the annealing behavior. At first isothermal annealing (at 80 °C for 0–180 min) followed by isochronal annealing (for 15 min between 100 °C and 190 °C in steps of 10 °C), studies had been performed in order to get information about the thermal stability of the interstitial boron and interstitial oxygen defect in 50- $\Omega $ cm material after irradiation with 23-GeV protons to a fluence of $6.91\times 10^{13}\,\,{\text {p/cm}^{2}}$. The results are presented and discussed. Furthermore, the extracted data from TSC measurements are compared with the macroscopic properties derived from current–voltage and capacitance–voltage characteristics. In addition, the introduction rate of interstitial boron and interstitial oxygen defect as a function of the initial doping concentration was determined by exposing diodes with different resistivities (10, 50, 250, and 2 $\text{k}\Omega $ cm) to 23-GeV protons. These results are compared with data from TSC and deep-level transient spectroscopy measurements achieved by the team of the CERN-RD50 “Acceptor removal project.” [ABSTRACT FROM AUTHOR]

Dynamic random access memory (DRAM) bits can be erroneously flipped when the row near the error bits is repeatedly accessed with the activate and precharge commands in a process called row hammering. The trap at an Si–SiO2 interface has been previously reported as the leading cause of such errors. The number of row hammering required for flipping bits initially decreases and then saturates with the increases in the row precharge time ($t_{\mathrm {RP}}$). The DRAM timing parameter is the time interval between an activate command and a precharge command. This study uses the saturation $t_{\mathrm {RP}}$ to estimate the electron emission time of the trap associated with a DRAM bit error. During $t_{\mathrm {RP}}$ time, the traps at the Si–SiO2 interface emit the trapped electrons. There are more chances of emission as $t_{\mathrm {RP}}$ increases, and less row hammering is needed. The emission time of a trapped electron is experimentally measured herein using commercial DDR4 components. The components are irradiated with gamma rays to induce the interface traps. The trap characteristics are then extracted without requiring an additional measurement setup with a device-level preparation. The trap energies with respect to the mid-band at the Si–SiO2 interface are 0.118–0.280 eV. The trap energies are distributed within approximately 5.6 kT energies at room temperature. [ABSTRACT FROM AUTHOR]

This article evaluates the data retention characteristics of irradiated multilevel-cell (MLC) 3-D NAND flash memories. We irradiated the memory chips by a Co-60 gamma-ray source for up to 50 krad(Si) and then wrote a random data pattern on the irradiated chips to find their retention characteristics. The experimental results show that the data retention property of the irradiated chips is significantly degraded when compared to the un-irradiated ones. We evaluated two independent strategies to improve the data retention characteristics of the irradiated chips. The first method involves high-temperature annealing of the irradiated chips, while the second method suggests preprogramming the memory modules before deploying them into radiation-prone environments. [ABSTRACT FROM AUTHOR]

Total-ionizing-dose effects are evaluated in vertical-charge-trapping NAND devices with silicon oxynitride (SiON) and SiO2 tunneling layers. Processing splits include SiON tunneling layers with and without H2/D2 high-pressure annealing. Programmed devices were irradiated to 500 krad(SiO2) with 10-keV X-rays and annealed for 30 min. Second programming after annealing does not fully restore the original, programmed state. Radiation-induced trapped holes compensate for deeply trapped electrons that are injected into the dielectric during device programming. Throughout the full irradiation and annealing sequence, threshold voltages remain large enough to enable successful nonvolatile (NV) memory application. [ABSTRACT FROM AUTHOR]

The synergetic effects of total ionization dose and high-temperature stress of silicon on insulator (SOI) FinFETs (FF) are investigated under ON-state bias condition. The experiments and TCAD simulations are employed to analyze the influence of different trapped-charges in the gate and buried oxide on the threshold voltage and mobility variations on the ON-state current of the devices. Results show that the threshold voltage degradation worsens for n-SOI FinFETs but weakens for the p-SOI FinFETs. Also, the ON-state current of n-SOI FinFETs is significantly enhanced, while the change of p-SOI FinFETs is weak under the synergetic effects. The threshold voltage degradation induced by synergetic effects for both n- and p-type SOI FinFETs can exceed the linear superposition of the two types of stresses, which may be related to the thermal release of trapped charges in the gate oxide. The enhanced degradation in the n-SOI FinFETs compared with the p-SOI FinFETs may result from the shallow energy level electron traps in HfO2. Besides, for both n- and p-type SOI FinFETs, the ON-state current variations under the synergetic effects depend on the competitive process of threshold voltage variation and the mobility fluctuation. [ABSTRACT FROM AUTHOR]

Room-temperature semiconductor radiation detectors (RTSDs) such as CdTe are becoming popular in computed tomography (CT) imaging. These detectors are often pixelated, requiring cumbersome postinteraction 3-D event reconstruction, which can benefit from detailed material characterization at the micron level. Transport properties and material defects with respect to electrons and holes are to be characterized, which is a labor-intensive process. Current state-of-the-art characterization is done either as a whole or at most pixel-by-pixel over the detector material. In this article, we propose a novel learning-based physical model to infer material properties at the microscopic level for RTSD. Our approach uses a novel physics-inspired learning model based on physical transport of charges with trapping centers for electrons and holes in the detector. The proposed model learns these material properties from known or measured input charges to the detector along with known or measured output signals and distributed charges in the bulk of the RTSD. The actual physical detector is divided into voxels in space and takes into account different material properties (such as drift, trapping, detrapping, and recombination) in each voxel as learnable model parameters. The model is based on a physics-inspired recurrent neural network model instead of traditional convolutional or fully connected networks. The advantage of our approach is the one-to-one relationship between the actual physical parameters of the voxels and learnable weights in the model, far fewer trainable parameters compared to traditional neural network approaches and less training time. The performance of our model has been evaluated on cadmium zinc telluride (CdZnTe), with voxels of three sizes, 25, 50, and $100~ \mu{\mathrm {m}}$ , for single charge input as well as multiple charge inputs at different voxel positions. Our learning-based model provides material properties with higher spatial resolution and performs well in all scenarios and matches the actual physical parameters better than state-of-the-art classical approaches. [ABSTRACT FROM AUTHOR]

The combined effects of proton irradiation and forward gate-bias stress on the interface traps of AlGaN/GaN heterostructure have been studied in this article. It is found that the effect of proton irradiation and forward gate-bias on the shift of flat band voltage $V_{\mathrm {FB}}$ is independent. By utilizing the frequency-dependent conductance technique, it is found that the trap density $D_{\mathrm {T}}$ at metal/AlGaN interface decreases after proton irradiation and the $D_{\mathrm {T}}$ at most energy levels increases after the following forward gate-bias. The $D_{\mathrm {T}}$ at AlGaN/GaN interface increases after proton irradiation and then decreases after the following forward gate-bias. The energy level range of metal/AlGaN interface traps reduces significantly under the forward gate-bias for the irradiated devices, however, that of AlGaN/GaN interface traps decreases little. In summary, the combined effect of proton irradiation and forward gate-bias stress on the interface traps is more complex than that on the bulk traps in AlGaN layer. [ABSTRACT FROM AUTHOR]

Germano-silicate fibers, mostly employed for telecom applications, are also implemented in radiation environments for data links or sensing. In this field, the understanding of radiation-induced mechanisms leading to the degradation of the performances of silica optical fibers has an essential role. Particularly, the estimation of the activation energies of the density of trapped states (DOTSs) governing the radiation-induced attenuation (RIA) is of primary importance. To investigate these mechanisms, the thermoluminescence (TL) is a powerful technique, by which the extrapolation of DOTSs has been previously largely achieved for pure and Al-, P-, Er-, and Yb-doped silica. Despite the key applications related to Ge-doped silica, one cannot do the same for this kind of fiber, due to an “anomalous” increase of their TL response along with the heating rate. The objective of this work is primarily to elucidate the specific radiation-induced mechanisms associated with the presence of Ge in silica that notably induce the anomalous TL response. We show from the experimental study of the RIA thermal annealing during the TL readout, and its correlation with the TL glow curve, that oxygen-deficient centers (ODCs) centers, trapping electrons during irradiation, form deep states which act as recombination center (RC) in the TL process. Finally, and most important, we propose a model that explains the TL anomalous features and how they are arisen from two specific properties of the annealing processes of Ge-related radiation-induced centers. [ABSTRACT FROM AUTHOR]

Total-ionizing-dose (TID) effects and low-frequency noise are evaluated in advanced bulk nMOS and pMOS FinFETs with SiO2/HfO2 gate dielectrics. Otherwise identical devices built with and without through-silicon via (TSV) integration exhibit threshold voltage shifts of less than 25 mV and changes in maximum transconductance of less than 1% up to 2 Mrad(SiO2). TSV integration negligibly impacts threshold shifts and degradation of subthreshold swing and $I_{\mathrm{\scriptscriptstyle ON}}/I_{\mathrm{\scriptscriptstyle OFF}}$ ratios. Similar low-frequency noise magnitudes and frequency dependencies are observed before and after TID irradiation for each device type. Effective densities of the near-interfacial electron traps responsible for the noise in the nMOS devices increase as the surface potential moves toward midgap, while effective densities of the hole traps that cause the noise in the pMOS devices increase as the surface potential moves toward the valence band edge. [ABSTRACT FROM AUTHOR]

Total-ionizing-dose (TID) effects are investigated for 22-nm fully-depleted silicon-on-insulator (FDSOI) and 14-nm bulk FinFET charge-trap memory transistors. Electron trapping in the gate dielectric establishes the programmed memory state for both silicon on insulator (SOI) and bulk devices. To first order, ionizing radiation does not interact strongly with programing-induced charges in the gate dielectric for either device type. Hole trapping in the buried oxide dominates the TID response of the 22-nm FDSOI devices. The 14-nm bulk devices with two fins and total effective fin widths of 150 nm are minimally affected by TID, but the subthreshold leakage of devices with 40 fins and total effective fin widths of $3~\mu \text{m}$ increases with increasing TID. When devices are programmed or reprogrammed after irradiation, significant increases in subthreshold slope are observed due to the generation of interface traps, border traps, and/or charge lateral nonuniformities. [ABSTRACT FROM AUTHOR]

We evaluate the sensitivity of neuromorphic inference accelerators based on silicon-oxide-nitride-oxide-silicon (SONOS) charge trap memory arrays to total ionizing dose (TID) effects. Data retention statistics were collected for 16 Mbit of 40-nm SONOS digital memory exposed to ionizing radiation from a Co-60 source, showing good retention of the bits up to the maximum dose of 500 krad(Si). Using this data, we formulate a rate-equation-based model for the TID response of trapped charge carriers in the ONO stack and predict the effect of TID on intermediate device states between “program” and “erase.” This model is then used to simulate arrays of low-power, analog SONOS devices that store 8-bit neural network weights and support in situ matrix–vector multiplication. We evaluate the accuracy of the irradiated SONOS-based inference accelerator on two image recognition tasks—CIFAR-10 and the challenging ImageNet data set—using state-of-the-art convolutional neural networks, such as ResNet-50. We find that across the data sets and neural networks evaluated, the accelerator tolerates a maximum TID between 10 and 100 krad(Si), with deeper networks being more susceptible to accuracy losses due to TID. [ABSTRACT FROM AUTHOR]

The total ionization dose (TID) effect and negative bias temperature instability (NBTI) effect of 130-nm partially-depleted silicon-on-insulator (PDSOI) MOSFETs fabricated on hardened wafers with silicon ion implantation and unhardened wafers are investigated. A TID-hardened PDSOI MOSFET up to 1 Mrad(Si) is obtained by Si+ implantation in buried oxide (BOX). The hardening benefits from the electron traps in the BOX introduced by Si+ implantation. Although the radiation hardening process has a rare impact on nominal electrical characteristics of the device before irradiation, it will affect the NBTI reliability, which is manifested as the decrease in the NBTI lifetime for the radiation-hardened devices. The energy distribution of positive charges built up during NBTI stress is obtained. It proves that more damage-related traps exist near the gate oxide/silicon interface for the radiation-hardened device, which accelerates the threshold voltage shift during the NBTI stress. This conclusion is also verified by the low-frequency noise characteristics. [ABSTRACT FROM AUTHOR]

In this article, we demonstrate the results of experimental and theoretical studies of F-centers in BaBrI single crystals. We have observed two types of F-centers related to an electron trapped in the iodine or bromine vacancy site. It was found that absorption bands due to F-centers can be induced either by radiation or additive coloration. The excitonic mechanism of F-center production was established and demonstrated. Optical properties of the F-centers in a monoclinic symmetry environment have been calculated by means of the embedded cluster method. [ABSTRACT FROM AUTHOR]

Coincidence time resolution (CTR) of scintillation detectors based on Ce- and Mg-codoped Gd3Al2Ga3O12 (GAGG) scintillation crystals and high-density silicon photomultipliers (SiPMs) is shown to be 165 ps (full width at half maximum) for 511-keV $\gamma $ -quanta, approaching that achieved by using LSO scintillators. To study the prospective for further improvement of the time resolution, the population of the emitting Ce centers was investigated by optical pump and probe technique using selective photoexcitation and probing by a white light continuum with subpicosecond time resolution. The importance of free electron trapping for excitation transfer to emitting Ce ions was revealed. The influence of transfer delay on the scintillation response time is described, and the dynamics of electron relaxation to the lowest excited level of Ce ion is studied experimentally and analyzed by taking into account intracenter relaxation and relaxation via conduction band. The influence of electron diffusivity on the rise time of the population of the emitting level is described. It is shown that codoping of GAGG:Ce by magnesium even at the level as low as 10 ppm efficiently decreases the scintillator response time by enhancing the electron diffusivity. [ABSTRACT FROM AUTHOR]

Laterally diffused metal–oxide–semiconductors transistors PD-silicon on insulator 150-nm mixed technology from Microchip are irradiated with 60Co gamma rays. Those irradiations have revealed a high sensitivity of the LDnMOS and LDpMOS pointing out that the main sensitive parameter is the ON-resistance. In this paper, degradation mechanisms at play are investigated through TCAD simulation, and an explanation of the physical mechanisms for the observed degradation is proposed. [ABSTRACT FROM AUTHOR]

This paper analyses the neutron irradiation impact on the electrical performances of unstressed, ON-state, OFF-state, and negative gate bias (NGB) stressed AlInN/GaN HEMTs. These irradiations have resulted in the creation of electron traps that are causing a decrease in the drain current and an increase in the access resistance of the unstressed, ON-state, or OFF-state stressed AlInN/GaN devices. These degradations have been correlated with gamma spectrometry measurements and transmutation reactions occurred during the thermalized neutron irradiation have been highlighted. Despite these phenomena, a rise in drain current and a reduction in access resistance have been observed when NGB stressed AlInN/GaN HEMTs were irradiated with a fluence of $1.2\times 10^{\mathbf {12}}$ neutrons/cm2. The differences between the electrical behaviors of unstressed, ON-state, OFF-state, and NGB stressed devices observed after the neutron bombardment are related to the presence of electron traps in these device structures. [ABSTRACT FROM AUTHOR]

We demonstrate that a new technique, near-zero field magnetoresistance (NZFMR) spectroscopy, can explore radiation damage in a wide variety of devices in a proof-of-concept study. The technique has great potential for the study of atomic-scale mechanisms of radiation damage in 3-D integrated circuits. In our study, we explore radiation damage in structures relevant to 3-D integrated circuits, but not on 3-D test structures themselves. Five structures of great technological importance to 3-D integrated circuits are investigated. We utilize both NZFMR and electrically detected magnetic resonance to investigate radiation effects in these structures. The structures involved in this paper are planar silicon metal–oxide–semiconductor field-effect transistors, silicon–germanium alloy-based transistors, fin-based transistors, silicon dioxide-based flowable oxides, and low-k dielectrics. Our study indicates that NZFMR has great potential in radiation damage studies, with exceptional promise in systems in which more conventional resonance is not possible. [ABSTRACT FROM AUTHOR]

Nondoped Cs2HfCl6 (CHC) and alkaline earth metal-doped CHC (AE:CHC) crystals were grown by the vertical Bridgman–Stockbarger method. The spectra of the AE:CHC under X-ray excitation were similar to those for the AE-free crystal; thus, AE doping did not change emission wavelength of CHC. We determined the light outputs and energy resolutions of nondoped CHC and AE:CHC by measuring pulse-height spectra under 662-keV gamma-ray excitation of a 137Cs source. Both light output and energy resolution were deteriorated with AE doping. For example, nondoped CHC had a light output of ~44 000 photons/MeV and energy resolution of ~5.2%; on the other hand, Sr 0.5 at.%-doped CHC had a light output of only ~28 000 photons/MeV and energy resolution of ~10%. Scintillation decay also did not change. The nonproportional response values of light output versus gamma-ray energy did not improve in AE:CHC either. Therefore, doped AEs can be responsible for creation of defect trap levels which would hamper the carrier transport in CHC structure. [ABSTRACT FROM AUTHOR]

The radiation hardness of AlGaN/GaN high-electron-mobility transistors (HEMTs) is found to improve with increasing GaN channel thickness. Epitaxial MgCaO shows promise as a radiation-tolerant gate dielectric, with only small shifts in operating parameters of metal–oxide–semiconductor HEMTs observed at doses up to 1 Mrad(SiO2). Bias-induced electron trapping and radiation-induced-hole trapping can occur in the MgCaO, depending on the applied bias during stress and/or irradiation. AC transconductance measurements are used to help understand charge trapping in these devices. [ABSTRACT FROM PUBLISHER]

Jupiter possesses the harshest trapped radiation environment in the solar system. Models of the Jovian-trapped radiation environment are a prerequisite for planning missions to this extreme environment. The high energy (>0.1 MeV for electrons and >1 MeV/nuc for protons and heavier ions) particle environment drives the shielding and microelectronic parts design for a spacecraft. Recently, models based on the measurements by the Galileo energetic particle detector and heavy ion counter have been updated for the trapped protons and heavy ions. The purpose of this paper is to describe these changes to the proton and heavy ion models and demonstrate their application to and relative impact on mission design. While trapped electrons at Jupiter dominate for total ionizing dose and displacement damage dose for typically shielded parts/materials (e.g., with ~100 mil or 2.54 mm of aluminum shielding), trapped protons can be a significant contributor to lightly shielded components (e.g., solar cells under 10–20 mil of cover glass). In contrast, although they will be described here for completeness, the Jovian-trapped heavy ions are typically not a driving environmental consideration for single event effects evaluations (their energies are so low that a small amount of shielding will attenuate the fluxes to levels below the interplanetary solar energetic particle and galactic cosmic rays). [ABSTRACT FROM PUBLISHER]

High electric field stress (HEFS) and annealing effects on irradiated (by 60Co $\gamma$ -ray) vertical double-diffused MOSFETs (VDMOSFETs) are investigated. The behaviors of the oxide-trapped charges and interface traps during the stress are measured by using a simplified midgap technique. Rapid recovery of the threshold voltage ( V_{\mathrm {th}} ) for the irradiated VDMOSFET is observed under a positive high electric field stress (PHEFS). The results show that the densities of oxide-trapped charges and interface traps decreased more rapidly for the PHEFS than that for postirradiation annealing. Repeated irradiation results of PHEFS-recovered VDMOSFETs indicate the possibility of reusing the irradiated VDMOSFETs. [ABSTRACT FROM AUTHOR]

Electrically active defects in high-purity semi-insulating (HPSI) 4H-silicon carbide (4H-SiC) X-ray detectors have been characterized before and after neutron irradiation by zero-bias thermally stimulated current (ZB-TSC) and high-temperature resistivity measurements. The ZB-TSC measurements prior to irradiation reveal nine hole traps in the energy range of 0.22–1.16 eV and two electron traps at \textEc -0.35 eV and \textEc -0.44 eV. For the same case, high-temperature resistivity measurements yield thermal activation energy in the range of 1–1.3 eV. It is considered that the hole traps at \textEv+ 0.83 eV and \textEv + 1.16 eV along with defects located near the activation energies are possibly responsible for the substrate compensation. A poor resolution of 11.8-keV full-width at half-maximum (at 40 keV of 152Eu) with un-irradiated HPSI 4H-SiC detectors is attributed to the charge trapping and polarization effects. After neutron irradiation at the fluence of 10^11 n/cm2, seven new traps ( \textEv+ 0.68 eV, \textEv + 1.08 eV, \textEv + 1.22 eV, \textEc -0.72 eV, \textEc - 0.9 eV, \textEc - 1.04 eV, and \textEc - 1.1 eV) are identified with no significant changes in the activation energies. This indicates that the substrate resistivity is unaffected by the neutron-irradiation-induced defects. No considerable changes in the X-ray spectral response are noted at 10^11 n/cm2. [ABSTRACT FROM PUBLISHER]

This paper shows the impact of low fluence neutron irradiation on AlInN/GaN HEMTs before and after a negative gate bias stress done at a gate-to-source voltage ( V\text {GS}) of −20 V and at a drain-to-source voltage ( V\text {DS}) of 0 V during 216 h. We have shown that the neutron irradiation induces a decrease in the drain current of 6% and an increase in access resistance of 8% for the unstressed component in opposite to the stressed component. In fact, a rise in drain current of 9% and no evolution of the access resistance have been observed for a stressed AlInN/GaN HEMT. This phenomenon is related to the formation of complex cluster between the electron traps induced by the aging test and those involved by the neutron irradiation. [ABSTRACT FROM PUBLISHER]

The emission of charge carriers from the interface traps as a function of irradiation dose and bias voltage is investigated in terms of Poole–Frenkel effect (PFE) used by deep-level transient spectroscopy (DLTS). The electrical properties in lateral PNP (LPNP) transistors caused by Co60 gamma-ray radiation are measured in situ during irradiation, showing that the interface traps give the main contribution to the excess base current of LPNP transistors. Based on the DLTS results, with increasing irradiation dose, the density of the charged positive interface traps at a given bias voltage increases. This causes an increase in the electric-field strength in the space-charge region and a decrease in the activation energy of interface traps and an increase in the emission rate of charge carriers from the interface traps, showing a similar feature to the classical PFE. However, the charge sign of the interface traps changes from negative to positive, which is different to the classical PFE, and thus displays a new mode of PFE. In order to confirm this conclusion, various bias conditions are employed during DLTS measurements. With decreasing the reverse bias, the electric-field strength increases, leading to an obvious decrease in activation energy of the interface traps and increase in emission rate of charge carriers. Moreover, the interface traps are shown to be uniformly located at the Si/SiO2 interface, and the uniformly distributed interface traps give the new PFE mode, which is independent of the position in depletion layer. [ABSTRACT FROM AUTHOR]

The influence of surface carrier concentration on the ideality factor of excess base current ( \Delta IB ) in gated lateral PNP (GLPNP) bipolar junction transistors (BJTs) induced by 1-MeV electrons is investigated. \Delta IB in LPNP BJTs is impacted by the surface carrier density and radiation-induced interface traps. In GLPNP BJTs, the surface carrier concentration can be controlled by the voltage applied to a gate over the base region. The ideality factor changes after irradiation, and its dependence on emitter-base voltage ( V\mathrm {EB} ) is a function of gate voltage. For the irradiated devices, as the gate voltage decreases from +20 to −5 V, the ideality factor for excess base current changes from a single slope to two-slope behavior. The majority carrier concentration at the surface of the base, controlled by the gate voltage, impacts the excess base current and its ideality factor. [ABSTRACT FROM AUTHOR]

We demonstrate a quantum transport model for total ionizing dose (TID) effects in graphene devices fabricated on silicon dioxide (SiO2). The scattering matrix method was used to compare transfer characteristics with experimental measurements. To match the pristine transfer curve, the contact on-site energy levels were pinned to +75 meV relative to the channel. TID effects were modeled by introducing positively charged traps throughout the gate oxide. Spatially resolved local density of states and particle current density reveal the effect of the Coulomb potential due to the positively charged traps. [ABSTRACT FROM PUBLISHER]

Electrically detected magnetic resonance (EDMR) measurements of 4H-SiC/SiO2 metal-oxide-semiconductor field-effect transistors (MOSFETs) show large changes in the EDMR induced by gamma irradiation, indicating substantial changes in interface structure but, surprisingly, no generation of interface dangling bond defects. Our results indicate substantial fundamental atomic scale differences between radiation responses of Si/SiO2 based MOSFETs and SiC/SiO2 based MOSFETs. [ABSTRACT FROM PUBLISHER]

Epitaxially grown La-based oxide has shown promise as a gate dielectric for GaAs substrate materials with a low interface trap density in the mid to low 10^11 cm ^\mathrm -2 eV ^\mathrm -1 range. Total ionizing dose (TID) effects have been studied on GaAs MOSFETs with Al2O3/La2O3 and Al2O3/La1.8Y0.2O3 gate oxides. Charge trapping mechanisms in GaAs MOSFETs are studied by the AC transconductance dispersion method. Al2O3/La2O3 gated devices show a combination of electron and hole trapping, whereas Al2O3/La1.8Y0.2O3 gated devices show primarily hole trapping. [ABSTRACT FROM PUBLISHER]

We have investigated the direct-current characteristics of the 130-nm partially depleted SOI NMOSFETs fabricated on modified wafer with silicon ion implantation and control wafer before and after total dose radiation. Due to the deep electron traps in buried oxide, the back gate threshold voltage of the modified SOI device increases when hot electrons are injected into the buried oxide. Moreover, due to this electrons injection process, the Top-Si/buried-oxide interface produces donor-like electron traps, which results in a kink effect in I - V characteristic curve and double gm peak behavior in back gate transistor. By TCAD simulation, we have demonstrated that the deformation of the I - $V$ curve depends on the density of the interface trap on the premise of double g_{m} peak generation. It was speculated that hot electrons injection could produce Si-O weak bond and weak interaction with the peculiar bonding parameter at the Top-Si/BOX interface. Finally, the radiation results show that silicon ion implantation can effectively enhance the radiation hardness performance of the SOI material. [ABSTRACT FROM PUBLISHER]

Defects located at the \text E\rm C - 1.1 (eV) level, which are electro-optically active deep traps, generally have been overlooked since their presence cannot be detected except for those in highly resistive CdTe compounds. The origin of this trap is still debated on whether it is from Te vacancies or from dislocations induced by secondary phase defects in Te. We have grown high-resistivity Te-rich CZT ingots to clarify the origin of the 1.1 eV defects and to analyze the defect levels in the CZT samples by current deep level transient spectroscopy (I-DLTS)and photoluminescence (PL). From the analysis, defect levels such as shallow acceptor/donor, A-centers, Cd vacancies and Te antisite appeared to be in both high and low concentrations of Te inclusions, but the level of 1.1-eV defects exhibited dependence on the density of Te inclusion in the CZT samples. We also evaluated the effect of the 1.1-eV deep-level defects on the detector’s performance in point view of carrier trapping and de-trapping. [ABSTRACT FROM PUBLISHER]

This work investigates the influence of alternate biasing on TID effects in mixed-signal programmable devices. By reducing the time the device is biased when exposed to ionizing radiation, the severity of TID effects is also reduced, due to the increasing in the initial recombination of electron-hole pairs and the radiation induced charge neutralization effect. These effects are investigated considering a switched capacitor filter prototyped in a Field Programmable Analog Array. Eight samples of such device were exposed to gamma radiation while the devices were alternately biased, by repeatedly turning the power on and off, corresponding to different equivalent total biasing times and duty-cycles. Results show increase in radiation tolerance to the alternate biased devices, which is dependent also on the biasing duty-cycle. Considering this behavior, a novel system level radiation hardening technique, based on modular redundancy, associated to an alternate biasing scheme, is also proposed in this paper. [ABSTRACT FROM PUBLISHER]

Total ionizing dose effects in hydrogen sensors based on metal-insulator-semiconductor field-effect transistor (MISFET) were investigated in this paper. The experimental results of influence electron irradiation on MISFET based on Pd-Ta2O5-SiO2-Si structure are presented. The models of hydrogen and radiation sensitivities of MISFET threshold voltage and electrical characteristics have been developed. These models can be used to interpret the experimental data, to estimate the critical doses and to forecast the performance of the hydrogen MISFET-sensors under action of ionizing radiation. [ABSTRACT FROM PUBLISHER]

The Switched Dose Rate technique is investigated when devices do not exhibit ELDRS. Experimental data and modeling results are presented and discussed in terms of hardness assurance. It is shown, for devices that do not show ELDRS, that a time is required before the switched devices reach the LDR curve. As a solution, it is proposed to apply an annealing between the HDR and the LDR irradiation. [ABSTRACT FROM PUBLISHER]

This paper shows the impact of low fluence neutron irradiation on AlGaN/GaN HEMTs, AlInN/GaN HEMTs and AlInN/GaN MOS-HEMTs. We have shown that the technological structure of devices and the presence of electron traps in the devices seems to play a major role on the evolution of dc electrical characteristics of irradiated GaN based transistors. After having degrading the electrical performances of AlGaN/GaN HEMTs with an electrical stress, we have shown that it is possible to improve the electrical characteristics of the stressed devices by a neutron irradiation. Moreover, we have also reported that the degradation induced by neutron irradiation is more important for the AlInN/GaN HEMTs with a gate interfacial oxide than for the AlInN/GaN HEMTs without a gate interfacial oxide. [ABSTRACT FROM PUBLISHER]

This paper presents analyses of polarization effects in ohmic and junction sensors by detailed three-dimensional modeling. It is shown for the example of compensated ${{\rm Cd}_{1 - {\rm x}}}{{\rm Zn}_{\rm x}}{\rm Te}$ detectors that the compensating deep-levels can be also responsible for both bias-induced and ionization-induced polarization phenomena. The capture cross sections of the deep levels are shown to play a dominant role in the formation of the polarizing space charge. Calculations show that bias-induced polarization is not expected to occur in ohmic MSM structures as long as the mobility remains constant. Ionization-induced polarization is expected to occur equally in ohmic and Schottky devices, but the sign and the distribution of the polarizing space charge depend on deep level cross sections. [ABSTRACT FROM AUTHOR]

The role and effect of stable Ce^4+ centers in Ce-doped LuAG single crystal scintillator is further studied by means of measurements of several optical, luminescence and scintillation characteristics. Two LuAG:Ce single crystal samples are compared: in one of them the dominating Ce^4 + center is stabilized by high concentration Mg^2+ codoping while the other one shows only the presence of stable Ce^3 + center. Tailored (Eu, Mg)–doped LuAG single crystal is also prepared to test the presence and thermal stability of hole traps in the host which affect the timing characteristics of Ce^4+ scintillation cycle, namely its restoration back to 4+ charge state in last step of the cycle. EPR experiment was also employed at Mg- and (Eu, Mg) doped LuAG samples and the signature of the O^ - hole center stabilized by Mg^2 + ion was clearly obtained. [ABSTRACT FROM AUTHOR]

The effects of \ Na^ + , \ Mg^2 + , \ Ca^2 + , \ Sr^2 + and \ Ba^2 + doping on the scintillation properties of \ CeBr_3 are evaluated in this paper. \ Ca^2 + and \ Sr^2 + doped \ CeBr_3 show different scintillation properties as compared to undoped \ CeBr_3, i.e. an additional perturbed \ Ce^3 + site with emission maxima red-shifted by 30 nm compared to unperturbed \ Ce^3 + sites as evidenced by X-ray excited emission and photoluminescence measurements. Also a nearly constant light yield at temperatures below 300 K, an increased decay time and the appearance of multiple glow peaks in thermoluminescence measurements are observed for Ca and Sr doped \ CeBr_3. These effects on the scintillation properties of \ CeBr_3 are explained using a single trap model where Br vacancies, formed as charge compensation for the aliovalent dopants, act as electron traps. [ABSTRACT FROM AUTHOR]

TCAD software for device modeling, called ECORCE, is presented. ECORCE is based on a classical drift-diffusion model and is distributed under the GPL. It facilitates TCAD modeling by providing an easy-to-use graphical user interface for defining the geometry and physical model of the devices, executing calculations, and analyzing results. Furthermore, by integrating a dynamic mesh generator, ECORCE frees the user from the meshing step for either DC or transient analysis. ECORCE allows Single Event Effect modeling and features a restricted diffusion add-on that accounts for the kinetics of the trapping-detrapping process in insulators. This paper demonstrates that ECORCE models the Single Event Effect and Total Ionizing Dose response of MOS devices. Experimental results are modeled quantitatively. [ABSTRACT FROM AUTHOR]

Current gain degradation in irradiated bipolar junction transistors is primarily due to excess base current caused by enhanced carrier recombination in the emitter-base space-charge region (SCR). Radiation-induced traps at the interface between silicon and the bipolar base oxide facilitate the recombination process primarily above the sensitive emitter-base junction. This leads to an increase in surface recombination current in the SCR, which is a non-ideal component of the BJT’s base current characteristic under active bias conditions. In this paper, we derive a precise analytical model for surface recombination current that captures bias dependencies typically omitted from traditional models. This improved model is validated by comparisons to these traditional approaches. [ABSTRACT FROM AUTHOR]

TCAD has been a useful tool for device design for decades. Radiation damage of devices requires accurate simulation of how charges move and are trapped, and the trap populations. This paper describes a simulation capability for these classes of problems and provides examples demonstrating its usefulness for investigation of device failure. [ABSTRACT FROM AUTHOR]

This paper presents a physics-based compact modeling approach that incorporates the impact of total ionizing dose (TID) and stress-induced defects into simulations of metal-oxide-semiconductor (MOS) devices and integrated circuits (ICs). This approach utilizes calculations of surface potential (\psi _s) to capture the charge contribution from oxide trapped charge and interface traps and to describe their impact on MOS electrostatics and device operating characteristics as a function of ionizing radiation exposure and aging effects. The modeling approach is demonstrated for bulk and silicon-on-insulator (SOI) MOS device. The formulation is verified using TCAD simulations and through the comparison of model calculations and experimental I - V characteristics from irradiated devices. The modeling approach is suitable for simulating TID and aging effects in advanced MOS devices and ICs, and is compatible with modern MOSFET compact modeling techniques. A circuit-level demonstration is given for TID and aging effects in SRAM cells. [ABSTRACT FROM AUTHOR]

Techniques based on bias switching during the irradiation allow to extend the measurement range of MOS dosimeters. To well predict the response of these sensors under operation conditions it is mandatory to understand the physical phenomena involved. A physics-based numerical model is presented here to reproduce the response of MOS dosimeters under switched bias irradiations. Reported non-monotonic responses after a bias switch were previously explained by the presence of two types of hole traps with different characteristic times. The model presented in this work shows that this behavior can be explained by the spatial charge redistribution using a single trap. The electric field dependences of hole capture and neutralization rates are analyzed and compared with previous experimental results and models in the literature. The spatial distribution of hole traps within the oxide is also analyzed. [ABSTRACT FROM AUTHOR]

Electrical stress and 10-keV x-ray irradiation and annealing responses are evaluated for back-gate MoS2 transistors. Relative stability of device characteristics is observed for constant-voltage stress. The drain current decreases significantly after both positive and negative bias irradiation. Density functional theory calculations and ozone exposure experiments suggest that O atoms adsorbed on the MoS2 surface during 10-keV x-ray irradiation function as electron traps, causing mobility degradation and voltage shifts. [ABSTRACT FROM PUBLISHER]

The total ionizing dose (TID) response of double-gate SiGe-SiO_2/HfO_2 \ pMOS FinFET devices is investigated under different device bias conditions. Negative bias irradiation leads to the worst-case degradation due to increased hole trapping in the HfO_2 layer, in contrast to what is typically observed for devices with SiO_2 or HfO_2 gate dielectrics. This occurs in the devices because radiation-induced holes that are generated in the SiO_2 interfacial layer can transport and become trapped in the HfO_2 under negative bias, leading to a more negative threshold voltage shift than observed at 0 V bias. Similarly, radiation-induced electrons that are generated in the SiO_2 interfacial layer can transport into the HfO_2 and become trapped under positive bias, leading to a more positive threshold voltage shift than observed at 0 V bias. [ABSTRACT FROM PUBLISHER]