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Forward and reverse HBM, MM, CDM ESD tests have been performed on 850-nm VCSELs, together with EOS and overpower test. The physical analysis of the tested devices showed a variety of damages not easily correlated to the measured electro-optical degradations. The solution requires the detailed interpretation of the observed physical mechanism, by means of electron microscopy and device modelling. [ABSTRACT FROM AUTHOR]

A recent model for laser diodes was applied to the decomposition of the experimental characteristics of several laser diodes into their fundamental components. This pointed out a problem involving the ideality factor and the clamp voltage. The two quantities indicate largely different values of the internal voltage, not explained or predicted by any theory. The solution of the puzzle requires going back to points as fundamental as the meaning of locality of band-to-band transitions in quantum or bulk active regions [ABSTRACT FROM AUTHOR]

A strong X-ray emission is one of the defining signatures of nuclear activity in galaxies. According to the Unified Model for Active Galactic Nuclei (AGN), both the X-ray radiation and the prominent broad emission lines, characterizing the optical and UV spectra of Type 1 AGNs, are originated in the innermost regions of the sources, close to the Super Massive Black Holes (SMBH), which power the central engine. Since the emission is concentrated in a very compact region (with typical size r ⩽ 0.1 pc) and it is not possible to obtain resolved images of the source, spectroscopic studies of this radiation represent the only valuable key to constrain the physical properties of matter and its structure in the center of active galaxies. Based on previous studies on the physics of the Broad Line Region (BLR) and on the X-ray spectra of broad (FWHM H β ⩾ 2000 km s −1 ) and narrow line (1000 km s −1 ⩽FWHM H β ⩽ 2000 km s −1 ) emitting objects, it has been observed that the kinematic and ionization properties of matter close to the SMBHs are related together, and, in particular, that ionization is higher in narrow line sources. Here we report on the study of the optical and X-ray spectra of a sample of Type 1 AGNs, selected from the Sloan Digital Sky Survey (SDSS) database, within an upper redshift limit of z = 0.35 , and detected at X-ray energies. We present analysis of the broad emission line fluxes and profiles, as well as the properties of the X-ray continuum and Fe K α emission and we use these parameters to assess the consistency of our current AGN understanding. [ABSTRACT FROM AUTHOR]

Highlights: [•] Trans-characteristics : the monitor current vs. laser voltage in a laser module. [•] They are shown to carry detailed information on the behavior of the active region. [•] Trans-characteristics are coupled with EBIC to study some laser burnout cases. [•] Basic concepts in laser diode theory are discussed, as gain and efficiency. [Copyright &y& Elsevier]

Highlights: [•] Optical gain is measured in single-mode devices by controlled change in optical losses. [•] The method is first applies to an ITLA and then to a DFB laser. [•] Degradation of an ITLA is explained by means of the new method. [•] Models are discussed dealing with threshold current. [Copyright &y& Elsevier]

Abstract: After recalling fundamentals of a recent model, the paper illustrates an application on a real device. The result is the measurement of a number of important parameters, related to physics and technology of a laser diode, which is in turn useful to address the failure analysis in case of degradation. [Copyright &y& Elsevier]

Abstract: The interpretation of the forward DC characteristics of LEDS and laser diodes is shown as a valuable tool to infer the internal structure of real devices and to address their analysis after failures. To this purpose, the self-consistent I(V) DC transfer function for the ideal laser diode is introduced. [Copyright &y& Elsevier]

Abstract: Three cases will point out as entire lots of unreliable microelectronic devices may reach the final user, without any warning. The conclusion is a warning against the many risks introduced for more and more small and medium end users of microelectronic devices by the lack of reliability culture. [Copyright &y& Elsevier]

Abstract: Silver–sulfur compounds have been detected at the internal lead frame of several commercial plastic packaged white LEDs that passed a standard incoming lot inspection but resulted all electrically open or degraded at the switching-on after mounting on the final boards. [Copyright &y& Elsevier]

Abstract: In this paper, ordinary FMEA (Failure Mode and Effects Analysis) was applied during the design phase of an electric motor control system for vehicle HVAC (Heating/Ventilation/Air Conditioning). The analysis of the field data from the second year forces to review FMEA. The corrective actions, planned on the basis of the sole failure mode, as usual in FMEA, proved to be inadequate and Failure Analysis was performed to understand the failure mechanism of the indicted component and integrate. New proper corrective actions were devised and successfully implemented. [Copyright &y& Elsevier]

Abstract: The paper describes a reliability prediction methodology that may be used to evaluate the reliability of electronics systems for industrial applications. The proposed methodology takes advantage of the potentiality of different reliability approaches. The aim of this new methodology is to minimize the deficiencies of the traditional reliability prediction methods calculating a corrective factor using the available field return data. In this way is possible to realize more realistic reliability assessment also in the case of new products or products without historic data. Applications of this prediction methodology on real electronic industrial systems are presented. [Copyright &y& Elsevier]

Antibiotics commonly used in the treatment of pigs – amoxicillin trihydrate, oxytetracycline hydrochloride and thiamphenicol – were added at different concentrations to aliquots of pig waste slurry plus anaerobic sludge in serum bottles. The biogas production and methane concentration in the headspace were monitored to determine the effect of the antibiotics on the anaerobic process. With thiamphenicol significant differences in methane production were found for concentrations of 80 and 160 mg l−1 slurry. Compared to the control, only minor differences in methane production were noted in the bottles to which amoxicillin (60 and 120 mg l−1) had been added. Methane production was about the same for the bottles with different oxytetracycline concentrations (125 and 250 mg l−1) and for the control. [Copyright &y& Elsevier]

A recent experiment used FIB to induce local modification in a single-mode edge emitting laser operating at 1310 nm, and led to a method for estimating gain parameters. In this experiment, the final FIB modification introduced large variation in electrical characteristics that were not analysed in detail, and even seemed to contradict the basic laser model that the experiment itself aimed to confirm. This paper focuses on this puzzling point, and solves it with a circuital hypothesis, a circuit simulation and a direct inspection by XEBIC. [ABSTRACT FROM AUTHOR]

Counterfeit electronics pose reliability risks and severe harms. The failures of systems that use counterfeits can cause safety and security problems. Lack of caution on the part of buyers, obsolescence, lower prices, costly inspection procedures, absence of origin verification tools is contributing to the widespread of counterfeit electronics. Two case studies are proposed to add a piece of information in this context supporting evidence regarding the capillary penetration of the counterfeit devices. It should contribute to arise some concerns. [ABSTRACT FROM AUTHOR]

Commercial GaN power amplifiers for RF applications, made of a pair of discrete transistors for operation in Doherty configuration, failed during the HAST tests. Failure Analysis pointed out a layout-specific issue related to thermal expansion at the level of the field plates. Anyway, the search for initial degradation stages using Optical Beam Induced Resistance Change and Photon Emission Microscopy revealed a subtle second mechanism, involving Ga interdiffusion into the gate metal lines, coming from hollow pipes in GaN. Both mechanisms are discussed. • Power GaN HEMTs for RF applications failed during environmental tests THB and HAST. • Field plate-related thermomechanical stress causes one of the two kinds of failures. • Alignment of hollow GaN pipes and Gate fingers leads to leaky paths. [ABSTRACT FROM AUTHOR]

Optical gain measurement is extended to chips designed for external cavity lasers, where facet reflectivity is intentionally kept null, which prevents from any application of the Hakki-Paoli method. The new method is first shown to be consistent with the standard methods, by applying it to a chip with Fabry-Perot resonances and comparing the results of the new and the Hakki-Paoli method. The validated new method is then applied to the non-reflecting cavity of a tunable laser diode based on external cavity. • Optical Gain measurement is proposed for non-reflecting cavities. • It stands on photon density calculation after a single-trip, and refers to a steady-state balance equation. • Results are compared between the new method and the consolidated Hakki Paoli method for a Fabry-Perot cavity. • Validation leads to absolute gain measurement in a real non-reflecting cavity. [ABSTRACT FROM AUTHOR]

The revision of the classic Hakki-Paoli method shows that the a priori knowledge of facet reflectivity and confinement factor is not required for measuring optical gain in semiconductor laser and LED emitters. Moreover, a recently proposed new formula for gain as a function of the applied voltage, combined with that method, allows for calculating the relevant parameters of the gain function by the sole sub-threshold spectral data. This avoids the known critical problems issued by instrument resolution on spectral data from the above-threshold domain. Moreover, this last chance allows for complete gain measurement also in degraded devices, when they do no more display any laser threshold, and then for including optical gain among the relevant parameters for monitoring device degradation. [ABSTRACT FROM AUTHOR]

Abstract: The water gas shift reaction (WGSR) is an attractive process for enhancing the conversion of syngas carbon monoxide contents into carbon dioxide and hydrogen by means of steam in medium- and small-scale coal gasification power plants integrated with Carbon Capture and Storage (CCS) technologies. Fixed bed gasifiers, in fact, may become an interesting solution for medium- and small-scale applications in distributed power generation, although a syngas with a low LHV (about 6–7MJ/kg), high N2 (40–45%) and low H2 content, is generated when air is used, as usual, as oxidant. Syngas LHV can be enhanced by using oxygen (or oxygen enriched air) instead of air. However, when oxygen is used an appropriate amount of diluent agent as additional steam, recirculated syngas or CO2 is fed into the gasifier to control gasification temperature. In the case of syngas recirculation, the gasification process produces a syngas characterized by a high CO2 content, suitable for a more efficient separation. This paper concerns the experimental investigation and numerical simulation of carbon monoxide conversion and hydrogen generation from WGSR, when high CO2 content operating mixtures are considered. A baseline mixture was assumed that simulates the fuel gas produced by coal gasification in a small-scale air-blown updraft gasifier. During the experiments the fraction of N2 in the baseline mixture was gradually replaced with increasing CO2 fraction in order to investigate its effects of CO2 concentration on reaction and catalysts performances. An experimental apparatus, designed and built at the Department of Mechanical Engineering of the University of Cagliari (DIMECA), was used to investigate the main performance of WGSR, using high CO2-content operating mixtures and different catalyst types (Fe/Cr or Pt/Al for high temperature and Cu/Zn or Pt/Al for low temperature), and varying fundamental parameters, such as residence time of reactants in the catalyst bed, reaction temperature and H2O/CO ratio. The experimental results are supported by an in-depth numerical analysis. Numerical simulations were carried out using zero-dimensional (CSTR-based equilibrium model), one-dimensional (PFR-based) and CFD two-dimensional computational models to characterize the spatial and time-dependent behavior of the process. [Copyright &y& Elsevier]

Solid state lighting systems have deeply penetrated the market and are widely available. White light emitting diodes (LEDs) are based on a gallium nitride blue-emitting chip and a phosphor-based layer is used to convert blue radiation to white light, in combination with an optical system to enhance light extraction. High temperatures can be detrimental for LED reliability, resulting in a gradual or catastrophic failure. Therefore, the design of such devices, especially in relation to use cases that require operation at high current and temperature levels, needs to be based on reliability considerations. In this work we analyze the robustness of high power white LEDs submitted to driving currents exceeding the nominal levels by means of electrical and optical characterization, as well as on failure analysis techniques. The results highlight a significant degradation of the main optical parameters (luminous flux, color coordinates, correlated color temperature, ...). Device cross sectioning highlighted a heavy darkening of the silicone material in the overstressed devices, and a delamination of the phosphors. Raman spectroscopy analysis highlighted an enhancement in luminescence of degraded samples. Such degradation was ascribed to the high temperature reached by the LEDs during the stress, that caused the degradation of the silicone lens; the process can be enhanced by the low efficiency of the phosphors and LEDs at high temperatures, resulting in a stronger heating of the devices. • High power leds • White leds • Solid state lighting • Robustness • Silicone degradation [ABSTRACT FROM AUTHOR]

Historically the aerospace market has always chosen high level reliability solutions through customized technologies and processes, in order to cope with the requirement driven by mission profiles and application environment severity. In parallel, Automotive market required more and more high reliability targets. As a consequence, the qualification activity has evolved, passing from a stress driven approach strictly based on AEC-Q100 standard to a failure mode driven approach oriented to satisfy the robustness criteria required by TIER1 and Car Makers. Starting from this scenario, new market opportunities for Automotive devices can be identified, since the most reliable of them are today eligible to be sold to aerospace manufacturers with important cost saving thanks to massive production volumes of consolidated technologies. A gap may still persist and has to be carefully explored. First of all, a study of the different application constraints has to be carried out and the potential failure modes activated by Aerospace cold unbalanced mission profile, atmospheric pressure and radiations have to be analysed. Experimental evidences have been collected as first step on advanced CMOS technologies, and their extension to the smart-power families, where digital and power coexist together, will be shortly discussed in this paper. [ABSTRACT FROM AUTHOR]

The study of solar cells subjected to reverse biasing is of fundamental importance since the reliability of an entire solar panel can be influenced by the presence of leakage paths on a single solar cell. The particular situation of reverse biasing can occur when, in a module, a solar cell is shadowed and the illuminated solar cells force the generated current through the shadowed solar cell that is reverse biased. The situation is further aggravated by the fact that reverse current crowds in localized shunt paths (“hot spots”) that are related to the presence of semiconductor defects. In this biasing condition the shadowed solar cell acts as a load and it can dissipate tens of watts with the risk of high temperature and damaging of the encapsulating materials. In this paper we study the effects of reverse biasing on metal wrap through (MWT) solar cells. This cell structure is particularly sensitive to reverse-bias, due to the presence of via holes in the junction. The presence of “hot spots” can be related to the through hole metallization pattern: this leads to the conclusion that the MWT production process may strongly affect the reliability of this technology and should be optimized to avoid the formation of parasitic reverse current paths in the crystal structure. [ABSTRACT FROM AUTHOR]

It is becoming clear that we can define two different types of nearby AGN belonging to the Seyfert 1 class (S1), on the basis of the match of the intensities of their Broad Balmer Lines (BBL) with the Boltzmann Plots (BP). These two types of S1 galaxies, that we call BP-S1 and NoBP-S1, are characterized, in first approximation, by Broad Line Regions (BLR) with different structural and physical properties. In this communication, we show that these features can be well pointed out by a multi-wavelength analysis of the continuum and of the broad recombination Hydrogen lines, that we carry out on a sample of objects detected at optical and X-ray frequencies. The investigation is addressed to verify whether BP-S1 are the ideal candidates for the study of the kinematical and structural properties of the BLR, in order to derive reliable estimates of the mass of their central engine and to constrain the properties of their nuclear continuum spectrum. [ABSTRACT FROM AUTHOR]

Highlights: [•] We describe the hot-plug phenomenon in LED modules. [•] We analyze the electrical nature of hot-plug current spikes. [•] We present a simplified model to characterize the in-rush current spikes. [•] We analyze the failure mechanisms of LEDs submitted to “hot-plugging” events. [Copyright &y& Elsevier]

Abstract: The aim of this work is to investigate the thermal stability of remote phosphor plates to be used in solid-state lighting systems, for the conversion of the blue light emitted by GaN-based LEDs into white light. A preliminary thermal characterization revealed that in normal conditions of blue light irradiance the phosphor plates can reach temperature levels higher than 60°C, which can affect both performance and reliability. The results of accelerated thermal stress tests indicate that high temperature levels can trigger a relevant degradation mechanism (estimated activation energy is 1.2eV), that drastically reduces the phosphor conversion efficiency and modifies the photometric and colorimetric characteristics of the emitted white light. [Copyright &y& Elsevier]

Abstract: Several early-stage field failures in systems mounting GaAs MMICs were specifically related to MIM capacitor failures. Failure analysis, in turn, classified the failed cases into three main categories, all referred to some weakness in the technological process. The relevant point is that such weak devices can reach the field at such a large scale, despite the very well known nature of their weakness. Ineffective screening at the Manufacturer’s plant is indicted for the problem. Lifetime prediction is attempted, on the user side, based on the detectability of the weak population. [Copyright &y& Elsevier]

Abstract: This paper presents a study of the high temperature degradation of high brightness light emitting diodes (HBLEDs) on gallium nitride. Two different families of devices, from two leading manufacturers, have been submitted to thermal stress: during treatment, the optical and electrical characteristics of the devices have been analyzed. Degradation modes detected after stress have been (i) operating voltage increase, (ii) output power decrease, (iii) modifications of the spectral properties. The degradation of the electrical and optical characteristics of the devices were found to have different kinetics: this fact indicates that optical power (OP) loss is not strongly related to the degradation of the electrical parameters of the LEDs. On the other hand, spectral analysis indicated that OP loss is strongly related to the decrease of the phosphors-related yellow emission band. Microscopic analysis showed that this effect can be ascribed to the carbonization of the package and phosphorous material. A degradation of the transparency of the top-side ohmic contact has been also detected after stress: these mechanisms are thought to be responsible for the detected OP decrease. OP decay process has been found to be thermally activated, with activation energy equal to 1.5eV. [Copyright &y& Elsevier]