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The Internet of Things (IoT) is becoming the future of the Internet with a large number of connected devices that are predicted to reach about 50 billion by 2020. With proliferation of IoT devices and need to increase information sharing in IoT applications, risk-based access control model has become the best candidate for both academic and commercial organizations to address access control issues. This model carries out a security risk analysis on the access request by using IoT contextual information to provide access decisions dynamically. This model solves challenges related to flexibility and scalability of the IoT system. Therefore, we propose an adaptive risk-based access control model for the IoT. This model uses real-time contextual information associated with the requesting user to calculate the security risk regarding each access request. It uses user attributes while making the access request, action severity, resource sensitivity and user risk history as inputs to analyze and calculate the risk value to determine the access decision. To detect abnormal and malicious actions, smart contracts are used to track and monitor user activities during the access session to detect and prevent potential security violations. In addition, as the risk estimation process is the essential stage to build a risk-based model, this paper provides a discussion of common risk estimation methods and then proposes the fuzzy inference system with expert judgment as to be the optimal approach to handle risk estimation process of the proposed risk-based model in the IoT system. [ABSTRACT FROM AUTHOR]

The effects of particle irradiation on the electrical properties of high efficiency p/n InP solar cells have been studied using a variety of techniques including current–voltage and spectral quantum efficiency measurements (QE), electron beam induced currents (EBIC), and deep level transient spectroscopy. A detailed analysis of the radiation response of the solar cell photovoltaic response is presented, and the primary damage mechanisms are identified. Data measured after irradiation by protons of various energies are correlated in terms of displacement damage dose to produce a characteristic degradation curve for the p/n InP technology. This characteristic curve is compared to that of the n/p InP technology to provide an assessment of the relative radiation hardness of the p/n devices. Radiation-induced decreases in the minority carrier diffusion length in both the p-type emitter and n-type base at low damage levels have been extracted from the QE and EBIC measurements, and damage coefficients have been determined. At high damage levels, EBIC profiles suggest that the primary device degradation mechanism is an increase in bulk resistivity due to electron trapping in the base. However, capacitance–voltage measurements did not indicate any change in the junction capacitance. A model to account for these effects based on radiation-induced defect kinetics is presented. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Abstract: This paper describes the forward technology solar cell experiment (FTSCE), which is a space experiment built by the Naval Research Laboratory (NRL) in collaboration with NASA Glenn Research Center (GRC), and the US Naval Academy (USNA) as part of the materials on the International Space Station (MISSE) program. The goal is to rapidly put current and future generation space solar cells on orbit and provide validation data for these technologies. Telemetry, command, control, and communication (TNC) for the FTSCE will be achieved through the Amateur Satellite Service using the PCSat2 system, which is an Amateur Radio system designed and built by the USNA. In addition to providing an off-the-shelf solution for FTSCE TNC, PCSat2 will provide a communications node for the Amateur Radio satellite system. The FTSCE and PCSat2 will be housed within the passive experiment container (PEC), which is an approximately 2ft×2ft×4in. metal container built by NASA Langley Research Center (NASA LaRC) as part of the MISSE program. NASA LaRC has also supplied a thin film materials experiment that will fly on the exterior of the thermal blanket covering the PCSat2. The PEC is planned to be transported to the ISS on a Shuttle flight. The PEC will be mounted on the exterior of the ISS by an astronaut during an extravehicular activity (EVA). After nominally 1 year, the PEC will be retrieved and returned to Earth. This paper presents the design of the experiment, the electrical data measured on the experiment solar cells, and the results of environmental testing of the system. [Copyright &y& Elsevier]

There is currently worldwide interest in developing silicon-based active optical components in order to leverage the infrastructure of silicon microelectronics technology for the fabrication of optoelectronic devices. Light emission in bulk silicon-based devices is constrained in wavelength to infrared emission, and in efficiency by the indirect bandgap of silicon. One promising strategy for overcoming these challenges is to make use of quantum-confined excitonic emission in silicon nanocrystals. A critical challenge for silicon nanocrystal devices based on nanocrystals embedded in silicon dioxide has been the development of a method for efficient electrical carrier injection. We report here a scheme for electrically pumping dense silicon nanocrystal arrays by a field-effect electroluminescence mechanism. In this excitation process, electrons and holes are both injected from the same semiconductor channel across a tunnelling barrier in a sequential programming process, in contrast to simultaneous carrier injection in conventional pn-junction light-emitting-diode structures. Light emission is strongly correlated with the injection of a second carrier into a nanocrystal that has been previously programmed with a charge of the opposite sign. [ABSTRACT FROM AUTHOR]

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

Explores a longstanding discrepancy between proton nonionizing energy loss (NIEL) calculations and experimental measurements in gallium arsenic devices. Displacement kerma and its relation to NIEL; Modified NIEL calculation; Discussion and conclusion.

Presents information on a study which analyzed the effect of proton irradiation of InGaAs/GaAs quantum-well (QW) light-emitting diodes (LED). Description of the device used; Sample irradiation and measurements; Data and analysis of QW LED; Comparison of proton damage coefficients.

We utilize bias-dependent internal photoemission spectroscopy to determine the metal/dielectric/silicon energy barrier profiles for Au/HfO2/Si and Au/Al2O3/Si structures. The results indicate that the applied voltage plays a large role in determining the effective barrier height and we attribute much of the variation in this case to image potential barrier lowering in measurements of single layers. By measuring current at both positive and negative voltages, we are able to measure the band offsets from Si and also to determine the flatband voltage and the barrier asymmetry at 0 V. Our SiO2 calibration sample yielded a conduction band offset value of 3.03±0.1 eV. Measurements on HfO2 give a conduction band offset value of 2.7±0.2 eV (at 1.0 V) and Al2O3 gives an offset of 3.3±0.1 (at 1.0 V). We believe that interfacial SiO2 layers may dominate the electron transport from silicon for these films. The Au/HfO2 barrier height was found to be 3.6±0.1 eV while the Au/Al2O3 barrier is 3.5±0.1 eV. [ABSTRACT FROM AUTHOR]

The effects of proton irradiation on strained InAs[sub x]P[sub 1-x]/InP-based quantum well solar cells (QWSCs) have been investigated by the electron beam induced current (EBIC) and cathodoluminescence (CL) techniques. From analysis of the EBIC data, capture rates within the quantum well region have been estimated, from which the open circuit voltages of the cells were calculated and shown to agree well with the measured values. Diffusion lengths have been estimated from analysis of both the EBIC and CL measurements. The location of the energy levels of proton-induced defects and their effectiveness as nonradiative recombination centers have been determined from Arrhenius plots of the total CL intensity emitted from the quantum wells following irradiation. The results suggest that deeper and narrower quantum wells increase the sensitivity of QWSCs to radiation damage. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The effect of an InP cap on the photoluminescence (PL) spectrum of an InGaAsP/InAlAs quantum well (QW) is investigated using excitation power and temperature dependent PL. An as-grown sample with the InP cap layer shows an inverted interface created between InP and InAlAs that has a transition energy very close to the transition energy of the QW; consequently, there is an overlap between them. On the other hand, the QW sample with the cap layer etched away does not have a feature due to the inverted interface; even at very low power, the only observed feature is due to the QW transition. [ABSTRACT FROM AUTHOR]

The simplicity of the hypertext model behind the World Wide Web is a factor in its success, but this simplicity brings limitations. One of these limitations is embedding links in documents. Open Hypermedia addresses this by instead storing them in separate link databases. Meanwhile, the Adaptive Hypermedia approach seeks to enhance a user's experience by inserting personalised additional content and links on the web page. However, these techniques do not offer the user any control over the adaptation. In this paper, we propose the concept of a multi-dimensional linkbase for adaptive links presentation. Links are created and stored in a single, multi-dimensional, linkbase that provides presentation links based on the user's preferences and profile. We present a web-based system Inquiry-led Personalised Navigation System that implements this multi-dimensional concept for controlling its personalisation of hyperlinks. We give the results of our evaluation, which confirm that user-controlled adaptation is a satisfactory approach to providing users with control over personalisation, and can alleviate the link overload problem. [ABSTRACT FROM AUTHOR]

We characterize radiation induced defects in n-type GaAs following electron, proton, and silicon ion irradiations using Deep Level Transient Spectroscopy (DLTS) and Electron Beam Induced Current (EBIC) measurements. EBIC micrographs show the existence of radiation induced recombination centers following high energy proton (E > 50 MeV) or 22 MeV silicon ion irradiations, which were not observed following 1 MeV electron or 2 MeV proton irradiations. The evolution of the U-band defect as deter- mined by DLTS seems to occur when active recombination centers are observed in the EBIC images and therefore, appears to be produced by high energy recoils probably creating defect clusters. [ABSTRACT FROM AUTHOR]

An analysis of the effects of low energy proton irradiation on the electrical performance of triple junction (3J) InGaP2/GaAs/Ge solar cells is presented. The Monte Carlo ion transport code SRIM is used to simulate the damage profile induced in a 3J solar cell under the conditions of typical ground testing and that of the omnidirectional space environment. The results are used to present a quantitative analysis of the defect, and hence damage, distribution induced in the cell active region by the different radiation conditions. The modeling results show that, in the space environment where the incident radiation is omnidirectional, the solar cell will experience a uniform damage distribution through the active region of the cell. The cases of directional spectrum irradiation and omnidirectional irradiation through very thin shielding are also considered. Through an application of the displacement damage dose analysis methodology, the implications of this result on mission performance predictions are investigated. [ABSTRACT FROM AUTHOR]

GaAs solar cells with different structures and polarities were irradiated with 1 and 5 MeV electrons. The energy dependence of the electron damage coefficients for the photocurrent, photovoltage, and maximum power were found to vary approximately linearly with NIEL in contrast to what has been found for other GaAs cells. [ABSTRACT FROM AUTHOR]

We present results of displacement damage correlation between 2 MeV protons and 22 MeV silicon ion irradiation damage in p+ n GaAs solar cells. The radiation induced degradation of the photovoltaic response correlates well in terms of displacement damage dose. [ABSTRACT FROM AUTHOR]

In order to expand the technology of III-V semiconductor devices with quantum structures to both terrestrial and space use, radiation induced defects as well as native defects generated in the quantum structures should be clarified. Electrically active defects in GaAs p+n diodes with embedded ten layers of InAs quantum dots (QDs) are investigated using Deep Level Transient Fourier Spectroscopy. Both majority carrier (electron) and minority carrier (hole) traps are characterized. In the devices of this study, GaP layers are embedded in between the QD layers to offset the compressive stress introduced during growth of InAs QDs. Devices are irradiated with high energy protons for three different fluences at room temperature in order to characterize radiation induced defects. Seven majority electron traps and one minority hole trap are found after proton irradiation. It is shown that four electron traps induced by proton irradiation increase in proportion to the fluence, whereas the EL2 trap, which appears before irradiation, is not affected by irradiation. These defects correspond to electron traps previously identified in GaAs. In addition, a 0.53 eV electron trap and a 0.14 eV hole trap are found in the QD layers before proton irradiation. It is shown that these native traps are also unaffected by irradiation. The nature of the 0.14 eV hole trap is thought to be Ga-vacancies in the GaP strain balancing layers. [ABSTRACT FROM AUTHOR]

A photoluminescence (PL) spectroscopy study of the bulk quaternary alloy InAlAsSb is presented. Samples were grown lattice-matched to InP by molecular beam epitaxy and two different growth temperatures of 450 °C and 325 °C were compared. Interpolated bandgap energies suggest that the development of this alloy would extend the range of available direct bandgaps attainable in materials lattice-matched to InP to energies as high as 1.81 eV. However, the peak energy of the observed PL emission is anomalously low for samples grown at both temperatures, with the 450 °C sample showing larger deviation from the expected bandgap. A fit of the integrated PL intensity (I) to an I ∞ Pk dependence, where P is the incident power density, yields characteristic coefficients k=1.05 and 1.18 for the 450 °C and 325 °C samples, respectively. This indicates that the PL from both samples is dominated by excitonic recombination. A blue-shift in the peak emission energy as a function of P, along with an S-shaped temperature dependence, is observed. These trends are characteristic of spatially-indirect recombination associated with compositional variations. The energy depth of the confining potential, as derived from the thermal quenching of the photoluminescence, is 0.14 eV for the 325 °C sample, which is consistent with the red-shift of the PL emission peak relative to the expected bandgap energy. This suggests that compositional variation is the primary cause of the anomalously low PL emission peak energy. The higher energy PL emission of the 325 °C sample, relative to the 450 °C sample, is consistent with a reduction of the compositional fluctuations. The lower growth temperature is therefore considered more favorable for further growth optimization. [ABSTRACT FROM AUTHOR]

The analytical drift-diffusion formalism is able to accurately simulate a wide range of solar cell architectures and was recently extended to include those with back surface reflectors. However, as solar cells approach the limits of material quality, photon recycling effects become increasingly important in predicting the behavior of these cells. In particular, the minority carrier diffusion length is significantly affected by the photon recycling, with consequences for the solar cell performance. In this paper, we outline an approach to account for photon recycling in the analytical Hovel model and compare analytical model predictions to GaAs-based experimental devices operating close to the fundamental efficiency limit. [ABSTRACT FROM AUTHOR]

The effects of ionizing radiation on the temperature-dependent conductivity of single-walled carbon nanotube (SWCNT) papers have been investigated in situ in a high vacuum environment. Irradiation of the SWCNT papers with 4.2 MeV alpha particles results in a steady decrease in the SWCNT paper conductivity, resulting in a 25% reduction in room temperature conductivity after a fluence of 3×1012 alpha particles/cm2. The radiation-induced temperature-dependent conductivity modification indicates that radiation damage causes an increase in the effective activation barrier for tunneling-like conductivity and a concomitant increase in wavefunction localization of charge carriers within individual SWCNTs. The spatial defect generation within the SWCNT paper was modeled and confirms that a uniform displacement damage dose was imparted to the paper. This allows the damage coefficient (i.e., differential change in conductivity with fluence) for alpha particles, carbon ions, and protons to be compared with the corresponding nonionizing energy loss (NIEL) of the incident particle. The resulting nonlinear relationship with NIEL between these parameters is distinct from the more typical linear response observed in many bulk semiconductors and superconductors and indicates that localized radiation damage in the SWCNT papers has a greater impact than distributed damage. Although SWCNT papers behave largely as a bulk material with properties that are a convolution of the underlying SWCNT distribution, the radiation response appears to be largely dominated by degradation in the preferred one-dimensional conduction within these two-dimensionally confined nanostructures. [ABSTRACT FROM AUTHOR]

Highlights • Epitaxial regrowth accomplished on a membrane that was removed from its native substrate. • Power-dependent photoluminescence shows comparable recombination rates versus baseline. • Cathodoluminescence map indicates uniform bulk crystal quality on membrane epitaxy. Abstract Micro-transfer printing has demonstrated value for device- and array-level heterogeneous integration in a variety of applications. Here, it is used instead to assemble unique substrates with the potential to enable III–V growth templates that are both low-cost and specified at any desired lattice parameter within the range of III–V materials. Critical to this, epitaxial growth crystal quality must be established as comparable to that produced on conventional epi-ready substrates. We demonstrate epitaxial regrowth on gallium arsenide membranes that were transfer printed from their source substrate and onto a target handle. Both morphology and luminescence properties were characterized. Comparing the transfer printed membrane epitaxy with epitaxy on a conventional substrate, we found recombination rates and spatial uniformity from power-dependent photoluminescence and cathodoluminescence, respectively, to yield similar results, suggesting material quality was not adversely limited by the engineered substrate. [ABSTRACT FROM AUTHOR]

The damage to diffused-junction n [sub +]-p InP solar cells induced by electron and proton irradiations over a wide range of energy from 0.5 to 3 MeV and 0.015 to 20 MeV, respectively, has been examined. The experimental electron and proton damage coefficients have been analyzed in terms of displacement damage dose, which is the product of the particle fluence and the calculated nonionizing energy loss [G. P. Summers, E. A. Burke, R. Shapiro, S. R. Messenger, and R. J. Walters, IEEE Trans. Nucl. Sci. 40, 1300 (1993).] Degradation of InP cells due to irradiation with electrons and protons with energies of more than 0.5 MeV show a single curve as a function of displacement damage dose. Based on the deep-level transient spectroscopy analysis, damage equivalence between electron and proton irradiation is discussed. InP solar cells are confirmed to be substantially more radiation resistant than Si and GaAs-on-Ge cells. [ABSTRACT FROM AUTHOR]

In this work, a multijunction solar cell is developed on a GaSb substrate that can efficiently convert the long-wavelength photons typically lost in a multijunction solar cell into electricity. A combination of modeling and experimental device development is used to optimize the performance of a dual junction GaSb/InGaAsSb concentrator solar cell. Using transfer printing, a commercially available GaAs-based triple junction cell is stacked mechanically with the GaSb-based materials to create a four-terminal, five junction cell with a spectral response range covering the region containing >99% of the available direct-beam power from the Sun reaching the surface of the Earth. The cell is assembled in a mini-module with a geometric concentration ratio of 744 suns on a two-axis tracking system and demonstrated a combined module efficiency of 41.2%, measured outdoors in Durham, NC. Taking into account the measured transmission of the optics gives an implied cell efficiency of 44.5%. [ABSTRACT FROM AUTHOR]

GaAs diode dark currents are correlated over a very large proton energy range as a function of displacement damage dose (DDD). The linearity of the dark current increase with DDD over a wide range of applied voltage bias deems this device an excellent candidate for a DD dosimeter. Additional proton testing performed in situ enabled error estimate determination to within 10% for simulated space use. [ABSTRACT FROM PUBLISHER]

Low-thrust geostationary transfer orbits (LT2GEO) are found to offer significant low cost options thus making them very attractive for GEO missions. However, LT2GEOs increase the transfer orbit time from days to months, thereby causing a significant increase in the time that satellites traverse the most intense trapped particle radiation belts. This paper describes the LT2GEO radiation environment and provides some practical implications using new solar cell technologies and materials. New solar cell and coverglass testing protocols are established using Monte Carlo transport modeling and experimental results are given for Qioptiq CMG borosilicate coverglass. [ABSTRACT FROM PUBLISHER]

Three-dimensional TCAD simulations are used for physics-based prediction of space radiation effects in III-V solar cells, and compared with experimentally measured characteristics of a p^+ n GaAs solar cell with AlGaAs window. Dark and illuminated I-V curves as well as corresponding performance parameters are computed and compared with experimental data for 2 MeV proton irradiation at various fluences. We analyze the role of majority and minority carrier traps in the solar cell performance degradation. The traps/defects parameters used in the simulations, for n-type and p-type GaAs, are derived from Deep Level Transient Spectroscopy (DLTS) data. The physics-based models allow a good match between simulation results and experimental data. However, assuming the device performance is dominated by a single recombination center is not adequate to completely capture the degradation mechanisms controlling the photovoltaic performance. [ABSTRACT FROM AUTHOR]

Three-dimensional TCAD simulations are used for physics-based prediction of space radiation effects in III-V solar cells, and compared with experimentally measured characteristics of a p^+ n GaAs solar cell with AlGaAs window. Dark and illuminated I-V curves as well as corresponding performance parameters are computed and compared with experimental data for 2 MeV proton irradiation at various fluences. We analyze the role of majority and minority carrier traps in the solar cell performance degradation. The traps/defects parameters used in the simulations, for n-type and p-type GaAs, are derived from Deep Level Transient Spectroscopy (DLTS) data. The physics-based models allow a good match between simulation results and experimental data. However, assuming the device performance is dominated by a single recombination center is not adequate to completely capture the degradation mechanisms controlling the photovoltaic performance. [ABSTRACT FROM PUBLISHER]

In this paper we extend the analytical drift-diffusion model, or Hovel model, to model the electrical characteristics of solar cells incorporating a back mirror. We use a compact summation approach to derive modified optical generation functions in Homojunction solar cells, considering both coherent and incoherent reflections from the back reflector. These modified generation functions are then used to derive analytical formulae for the current–voltage characteristics of mirrored solar cells. We simulate the quantum efficiency of a simple GaAs np diode with a planar gold back reflector, and compare the results with the standard Hovel model using a generation function given by the Beer–Lambert law. Finally, we use the model to simulate the performance of a real GaAs solar cell device fabricated using an epitaxial-lift-off procedure, demonstrating excellent agreement between the simulated and measured characteristics. [ABSTRACT FROM PUBLISHER]

Abstract: Electroluminescence measured at different injection current densities is used to study the effect of particle irradiation on GaInP/GaInAs/Ge triple-junction solar cells. By employing the optoelectronic reciprocity relation, the irradiation-induced degradation in the J–V characteristics of all individual subcells and their underlying diode saturation parameters is derived. Also, the dependence of the solar cell irradiation response on the position of the irradiation-induced non-radiative recombination centers within the cell active region, i.e., the quasi-neutral regions and the space charge region, is discussed. [Copyright &y& Elsevier]

Lattice matched InAlGaAs tunnel junctions with a 1.18 eV bandgap have been grown for a triple-junction solar cell on InP. By including two InGaAs quantum wells in the structure, a peak tunnel current density of 113 A/cm2 was observed, 45 times greater than the baseline bulk InAlGaAs tunnel junction. The differential resistance of the quantum well device is 7.52 × 10-4 Ω cm2, a 15-fold improvement over the baseline device. The transmission loss to the bottom cell is estimated to be approximately 1.7% and a network simulation demonstrates that quantum well tunnel junctions play a key role in improving performance at high sun-concentrations. [ABSTRACT FROM AUTHOR]

BDD-IIR radiation environment detector data are used to calculate the expected solar array degradation for over 9 years of GPS orbit and compared with telemetered solar array data. The large discrepancy between the predicted and measured solar array output remains, thereby eliminating displacement damage as the sole damage mechanism to the solar arrays. [ABSTRACT FROM PUBLISHER]

MCNPX Monte Carlo electron transport analyses are used to characterize the electron beam facility at NEO Beam. The electron flux and energy profiles are quantified along the beam path leading to a better understanding of solar cell damage. Experimental results are compared to the MCNPX simulations. [ABSTRACT FROM AUTHOR]

We report the results of the characterization of irradiated InGaP2/GaAs/Ge multijunction (MJ) solar cells using the cathodoluminescence (CL) imaging/spectroscopy and electron beam induced current (EBIC) modes of scanning electron microscopy (SEM). These techniques were applied to verify the influence of irradiation damage on the optoelectronic properties of each subcell in the monolithic MJ structure and correlate them with the illuminated (AM0, 1 sun, 25^\circC) current–voltage (I–V) and quantum efficiency (QE) measurements. Minority carrier lifetime degradation data from CL measurements confirm that the GaAs subcell dominates the overall degradation of the 3J device. Also, a carrier removal mechanism in the GaAs subcell was revealed from the EBIC/CL measurements. [ABSTRACT FROM AUTHOR]

Defects produced by 0.6 MeV, 1 MeV and 5 MeV electrons are compared with those produced by 2 MeV proton irradiations in \ p ^+ \ n GaAs diodes using Deep Level Transient Spectroscopy (DLTS). Following 0.6 and 1 MeV electron irradiation, the measured DLTS spectra matched that of the literature. After 5 MeV electron irradiation, however, a new DLTS peak was observed. The new peak is located on the low temperature side of the common E3 peak. This new electron-induced DLTS peak is assigned to be the same peak produced by proton irradiation and commonly labeled PR4^\prime\prime. Further analysis of the DLTS data indicate that the PR4^\prime\prime peak is independent of the displacement damage dose deposited but is dependent on the primary recoil energy. [ABSTRACT FROM PUBLISHER]

Electrical and structural changes in GaAs are monitored using electron beam induced current (EBIC) and transmission electron microscopy (TEM) measurements after irradiation by protons and silicon ions. It has been determined that higher energy protons (E ges 10 MeV) and silicon ions disordered regions that are electrically and structurally different than those produced by lower energy protons. The data suggest that these disordered regions are responsible for causing the deviations between experimental data and NIEL. From analyses of the recoil spectra, high energy recoils appear to be responsible for the formation of these disordered regions. [ABSTRACT FROM PUBLISHER]

An index that would reliably rank the relative radiation hardness of semiconductors would be very helpful for selecting materials for many applications. The concept of "concentration of primary defects" (CPD) has been proposed as such an index. Here we show that for the GaAs-InP family of semiconductors used in solar cells, CPD yields results that do not agree with experiment. The long-established concept of damage constants for various semiconductor properties is a more reliable index. For solar cells the relevant damage constant is that for the degradation of minority carrier lifetime. Although the damage constants reported for different semiconductors are specific to a particular type and energy of radiation, we show they can be extended beyond the type and particle energy for which they were originally determined by using nonionizing energy loss (NIEL), thereby greatly extending their possible application. [ABSTRACT FROM AUTHOR]

The effect of incident particle range, straggling, primary recoil atom range and target volume on the expected applicability of nonionizing energy loss (NIEL) as a basis for correlating displacement damage effects are quantified. Examples are given for protons and alpha particles incident on both silicon and gallium arsenide. [ABSTRACT FROM AUTHOR]

Gallium nitride (GaN)-based blue-emitting diodes (CREE Model C430-DH8S) were irradiated at room temperature with protons in the energy range 2 to 115 MeV at fluences varying from 1 × 1011 to 1 × 1015 cm-2. Light output degradation curves were obtained for each energy and the damage constant (A) associated with these curves was determined according to the theory of Rose and Barnes. For proton energies less than 10 MeV, A varies inversely with the proton energy (E). At higher energies, A is consistently above the 1/E relationship. The change in nature of the energy dependence is attributed to nuclear interactions. Nonionizing energy loss calculations for the case of protons on GaN are presented. Good agreement between theory and experiment is obtained. [ABSTRACT FROM AUTHOR]

The proton-induced nonionizing energy loss (NIEL) for representative device materials are presented for the energy range between the displacement damage threshold to 1 GeV. All interaction mechanisms (Coulomb and nuclear elastic/nonelastic) are fully accounted for in the present NIEL calculations. For Coulomb interactions, the Ziegler-Biersack-Littmark (ZBL) screened potential was used in the lower energy range (<50MeV) and the relativistic formulation was used in the higher energy range (< 50 MeV). A charged particle transport code, MCNPX, was used to compute the NIEL due to nuclear interactions. [ABSTRACT FROM AUTHOR]

We describe an analytical model for calculating nonionizing energy loss (NIEL) for heavy ions based on screened Coulomb potentials in the nonrelativistic limit. The model applies to any incident ion on any target material where the Coulomb interaction is primarily responsible for atomic displacement. Results are compared with previous methods of extracting NIEL from Monte Carlo SRIM runs. Examples of NIEL calculations are given for incident ions having energies ranging from the threshold for atomic displacement to 1 GeV. The incident ions Include H, He, B, Si, Fe, Xe, and Au. Example targets include Si, GaAs, InP, and SiC. [ABSTRACT FROM AUTHOR]

Presents a study that examined the quantitative modeling of the response of silicon solar cells to protons with energies below several megaelectronvolts by taking into account the total energy deposited in the active region as the proton slows down. Background on the concept of displacement damage dose; Investigation of the application of the displacement damage dose method to silicon solar cells; Analysis of the application to displacement damage dose analysis.