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InGaAs-InAlAs strained-layer superlattices, with both controlled strain magnitude and direction in the narrower gap layers, were grown by molecular beam epitaxy. Exciton related peaks and steplike structures in transmission spectra were clearly observed even at room temperature. The close agreement of these observed peak positions with theoretical calculations indicates that heavy-hole and light-hole level reversal was attained in the tensile-strained narrower gap layers. [ABSTRACT FROM AUTHOR]

Abstract: The valence states of the Mn ions in Pr1−x A x MnO3−δ (A=Ca, Sr) are investigated by Mn-L3 X-ray absorption near-edge structure (XANES) analysis. The spectral fine structures in the Mn-L3 XANES analysis show a significant difference between Pr0.5Ca0.5MnO3−δ and Pr0.5Sr0.5MnO3−δ , a paramagnetic insulator and a ferromagnetic metal, respectively, at room temperature, whereas the spectral structures of Pr0.7Ca0.3MnO3−δ and Pr0.7Sr0.3MnO3−δ , paramagnetic insulators, are almost identical. These results indicate that the valence states of the Mn ions in these materials are highly correlated with their magnetic and electrical properties. A significant difference was also found between the Mn-L3 XANES profiles of Pr1−x Ca x MnO3−δ and the profiles formed by the linear combination of the Mn-L3 XANES spectra of PrMnO3 (Mn3+) and CaMnO3 (Mn4+). This difference indicates that the Mn ions in these materials do not have a mixed-valence state of 3+ and 4+, but have an intermediate valence state o 3+ and 4+. [Copyright &y& Elsevier]

SET-induced soft-error rates (SERSETS) of logic LSIs are estimated from SET pulse-widths measured in logic cells used in logic LSIs. The estimated rates are consistent with directly measured SERSETS for logic LSIs. [ABSTRACT FROM AUTHOR]

Single event transient (SET) pulse-widths were measured as a function of linear energy transfer (LET) by using pulse capture circuits and simulated with mixed-mode 3-D device simulations. We found that the carrier recombination process dominates the LET dependence of the pulse-widths. [ABSTRACT FROM AUTHOR]

Described is an estimation technique of single event transient voltage pulses in VLSI circuits from heavy-ion-induced transient currents measured in a single MOSFET. Waveforms of the transient voltage pulses are fully estimated by using transient current data obtained in various drain voltage conditions. Modeling of the irradiated device behavior for use in device/circuit simulations is not required. The concept is validated using a 2-D mixed-mode device simulation. [ABSTRACT FROM AUTHOR]

The effects of buried-well potential perturbation under the buried-oxide (BOX) layer are studied in both a heavy-ion single event upset (SEU) test and a high-energy proton-SEU test of a silicon-on-insulator (SOI) dual interlocked storage cell (DICE)-based flip-flop. Their dependence on incident angle and back bias is discussed. We fabricated both DICE-based flip-flop and conventional flip-flop, which are designed as 80 000-stage shift-register chains. In a heavy-ion test, a considerable number of SEUs were observed at back bias exceeding 2.4 V, and a ten-times larger SEU-cross section was finally recorded at back bias of 3.0 V compared with the total active area of a DICE-based flip-flop cell. This marks the first case where DICE topology was found to be broken by buried-well potential perturbation on an SOI DICE-based flip-flop. In a proton test, one error was observed at back bias of 2.0 V. The SEU rate in the Van Allen belt at an altitude of 2300 km and an inclination of 90° was estimated as being once every 5 years. [ABSTRACT FROM AUTHOR]

Single-event upset (SEU) hardness varies across dies, wafers, and lots—even just after fabrication and further across time. Mechanisms of postfabrication variations include total ionizing dose (TID) effects, which are caused by long-term radiation exposure. This synergistic effect of TID on SEU hardness is a particular concern in integrated circuits used in space and nuclear radiation environments. This article shows that an electrical parameter called the data-retention voltage is useful in dealing with such TID effects on the SEU hardness of static random access memories (SRAMs), which are known to be particularly radiation-sensitive. Experiments showed that TID-induced variations in SRAM SEU hardness, i.e., variations in SEU cross sections, were predicted by measuring the data-retention voltage. In addition, these variations were canceled out by adjusting the power supply voltage according to its interesting relationship to the data-retention voltage. Results suggest that it might be possible in flight to predict and cancel out SEU hardness variations caused by TID and other synergistic effects. [ABSTRACT FROM AUTHOR]

We have investigated the effect of homogenous uniaxial and biaxial strains on the thermal oxidation processes of Si with newly developed techniques. X-ray photoelectron spectroscopy (XPS) and ellipsometry measurements have revealed that the biaxial compressive strain suppresses the oxidation rate at temperatures lower than 800 °C, while the uniaxial strain does not affect the oxidation rate. It has been also found that stress during the thermal oxidation does not cause any change in the electronic states of the oxide which are characterized by XPS and x-ray absorption near edge structure. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Organic solar cells have attractive potential for space applications as they have very high specific power (power generated per weight) and ultra-high flexibility (to reduce stowed volume). However, one critical issue is whether they are stable under the harsh space environment, particularly their stability under high energy, high flux, electron and proton bombardment. In this paper, the stability of benchmark organic photovoltaic layers under proton bombardment (150 keV with a fluence of 1 × 1012/cm2) and electron bombardment (1 MeV with a fluence of 1 × 1013/cm2) under vacuum is investigated. Raman spectroscopy, photoluminescence spectroscopy, and optical reflectance spectroscopy are applied to study their chemical/structural, photo-chemical/morphological, and optical stability after the bombardments. The results show that all the benchmark organic photovoltaic films are stable under the radiation, implying that organic solar cells could be feasible for space applications. [ABSTRACT FROM AUTHOR]

Single-event upsets induced by multiple-cell charge generation are studied in a 20-nm bulk SRAM by performing laser irradiation tests. The single-pulse two-photon absorption is utilized to simulate charge generation over multiple SRAM cells. The analysis of fail bit maps reveals that the physical topology of fail bits strongly depends on data patterns stored in SRAM cells. Our results indicate that potential perturbations in multiple p-wells play a key role in determining fail bit patterns. A novel multiple-cell upset mechanism, named multi-well coupled potential unbalancing, is proposed based on the consideration of the unbalanced activation of parasitic bipolar effects. The dominance of this mechanism is confirmed through multiple-pulse irradiation tests. [ABSTRACT FROM AUTHOR]

The breakdown electric field of several SiC polymorphs has been investigated theoretically using a concept of “recovery rate,” which is obtained by first principles calculations. A good relationship between the experimental breakdown electric fields and the calculated recovery rate of 4H-, 6H-, and 3C-SiC was obtained. In order to examine the stability of SiC polymorphs, the total electronic energies of various types of SiC crystal structures were calculated. Here, two candidates of polymorphs—GeS-type- and 2H-SiC—with energies comparable to those of experimentally well-established structures, have been obtained. The breakdown electric fields of these two polymorphs were estimated using a relationship obtained from the results of 4H-, 6H-, and 3C-SiC. This indicates that one of these polymorphs, GeS-type-SiC, has higher breakdown electric field than any other SiC polymorphs. In addition to the investigation with the recovery rate, relationship between experimental breakdown electric field and calculated band gap with recently developed accurate electron-correlation potential has been also discussed. [ABSTRACT FROM AUTHOR]

An interesting multiple-cell upset (MCU) phenomenon in silicon-on-insulator (SOI) static random access memorys (SRAMs) featuring long lines of more than ten flipped cells is studied. Such an abnormal MCU phenomenon was recently observed for back-biased SOI SRAMs in a heavy-ion test. Using a two-photon absorption-based laser system, we performed fixed-point observations and visualized the development of long line-type MCUs with increasing back bias. The visualization results provided insights to elucidate the mechanism behind these phenomena. Furthermore, using fixed-point observations, we extracted the length of MCUs for various bias conditions and laser strike positions. It was found that for all cases studied, the line length could be explained using an analytical model. [ABSTRACT FROM PUBLISHER]

The impact of semiconductor process scaling on the overall transient response of SiGe BiCMOS platforms is investigated. Pulsed-laser two-photon absorption (TPA) and heavy-ion broad-beam testing of SiGe HBT device and digital test structures across several generations of SiGe technologies are utilized to investigate the potential impacts of semiconductor process scaling (e.g., lateral/vertical scaling, changes in doping, Ge content, etc.) on the overall transient shape, magnitude, and duration. Technology scaling is shown to increase the single-event effect (SEE) sensitivity of SiGe HBTs (i.e., elevated collected charge, where 1st Gen. QC <3 rd Gen. QC <4 th Gen. QC ). Modern third-generation and fourth-generation devices under a forward-active bias (i.e., forward-biased EB junction, reverse-biased CB junction) exhibit a large diffusive transient component between the emitter and collector terminals, driving an elevation in collected charge. 3-D TCAD modeling is utilized to understand the fundamental transient mechanisms and assess the primary scaling factors affecting SEE sensitivity. Ion-strike simulations show that bulk traps can substantially enhance the charge collection mechanisms within these devices. These results suggest that SiGe technology scaling may have a strong impact on the radiation-induced transient response of SiGe HBTs, with future SiGe technology generations potentially exhibiting increased sensitivities to single-event effects. [ABSTRACT FROM PUBLISHER]

Abstract: We have investigated the effect of In diffusion on the electronic structure of a polyethylenedioxythiophene-poly (styrenesulfonate) layer deposited on InSnxO1−x substrate by photoelectron spectroscopy. We observe additional states near the highest occupied molecular orbital of the polymer layer that are generated by In releases from the substrate. Also, we observe that In diffusion continues into an overlayer of a mixture of poly(3-hexylthiophene) and [6,6]-phenyl C61-butyric acid methyl ester. On the basis of the results of the numerical line shape analysis of In 3d5/2 core level emission, we rule out the presence of metallic In clusters within the organic layers and suggest instead that In/sulfur compounds are present within the organic layers. [Copyright &y& Elsevier]

A scan flip-flop (FF) is designed to observe both single event transient (SET) and single event upset (SEU) soft errors in logic VLSI systems. The SET and SEU soft errors mean the upset caused by latching an SET pulse that originates in combinational logic blocks and the upset caused by a direct ion hit to the FF, respectively. An irradiation test method using the scan FF is proposed to obtain SET and SEU soft-error rates at each FF distributed in logic VLSI systems. A test chip is designed using a 0.2-µm fully-depleted silicon-on-insulator standard cell library. The basic concepts have been validated with Verilog timing simulations. The cell-level implementation costs of the proposed scan FF are estimated to be reasonable. [ABSTRACT FROM AUTHOR]

Current components of heavy-ion-induced transient currents in a 0.2-μm fully-depleted SOI MOSFET are analyzed in the time domain. The analysis demonstrates that the transient currents have another slow-decay current component that is different from the two conventional current components: a prompt discharge current and a slow-decay parasitic bipolar current. The stow-decay component revealed here is a flow of deposited carriers stored in the body region to maintain quasi-neutrality, and it drastically widens the transient pulse. [ABSTRACT FROM AUTHOR]

Lead halide perovskite single layers with three grain sizes are subjected to proton-beam irradiation in order to assess the durability and radiation tolerance of perovskite solar cells (PSCs) against space radiation. Proton-beam irradiation is chosen because proton beams significantly affect solar cell performance in the space environment. We evaluate the effects of proton beams by focusing on the grain structure, crystal structure, and carrier lifetime of a perovskite single layer by using scanning electron microscopy, X-ray diffraction, photoluminescence (PL) spectra, and time-resolved PL (TRPL). The results show that proton irradiation does not significantly affect the grain structure and crystal structure of perovskite layer; the TRPL results show that the carrier lifetime inside the grain is constant up to a fluence of 1 × 10 14 p + /cm 2 and decreases significantly at a fluence of 1 × 10 15 p + /cm 2 . Proton-beam radiation tolerance of the grain inside the perovskite layer is dominant in the radiation tolerance of PSCs.