optical measurement techniques of recombination lifetime based on the free carriers absorption effect

We review successful measurement techniques for the evaluation of the recombination properties in semiconductor materials based on the optically induced free carrier absorption. All the methodologies presented share the common feature of exploiting a laser beam to excite electron-hole pairs within the volume of the sample under investigation, while the probing methods can vary according to the different methodology analyzed. As recombination properties are of paramount importance in determining the properties of semiconductor devices (i.e, bipolar transistor gain, power devices switching features, and solar cells efficiency), their knowledge allows for better understanding of experimental results and robust TCAD simulator calibration. Being contactless and applicable without any particular preparation of the sample under investigation, they have been considered attractive to monitor these parameters inline or just after production of many different semiconductor devices

Electrically induced Bragg Reflectors in In/InGaAsP waveguides as ultrafast optoelectronic modulators

In this paper, with the help of numerical simulations, we show how it is possible to create a Distributed Bragg Reflector by electrically inducing periodical refractive index variations in unperturbed III-V rib-waveguides to design different kind of devices. This approach allows to induce the optoelectronic devices by a suitable reconfiguration of the potential applied to the electrode matrix, i.e. to have a defined routing/switching matrix, or, for dynamic applications, realize intensity modulators, capable of reaching a theoretical 40 GHz switching speed

Management of Symptomatic Venous Aneurysm

Venous aneurysms (VAs) have been described in quite of all the major veins. They represent uncommon events but often life-threatening because of pulmonary or paradoxical embolism. We describe our twelve patients' series with acute pulmonary emboli due to venous aneurysm thrombosis. Our experience underlines the importance of a multilevel case-by-case approach and the immediate venous lower limbs duplex scan evaluation in pulmonary embolism events. Our data confirm that anticoagulant alone is not effective in preventing pulmonary embolism. We believe that all the VAs of the deep venous system of the extremities should be treated with surgery as well as symptomatic superficial venous aneurysm. A simple excision can significantly improve symptoms and prevent pulmonary embolism

study on the spatial generation of breakdown spots in mim capacitors with different aspect ratios

Metal-insulator-metal (MIM) large area (>10 -4 cm 2 ) capacitors with different aspect ratios were subjected to severe stress conditions (Eox>4-5 MV/cm) with the aim of generating a large density of breakdown spots (from 10 5 to 10 6 spots/cm 2 ) in the same device. The resulting mark pattern on the top metal electrode associated with the failure events was analyzed first using conventional functional estimators for two- dimensional spatial statistics. Second, as a double check, the attention was focused on the same breakdown spot patterns but in relation to the probe point location. In this latter case, the objective was to rule out any stochastic dependence of the breakdown spot distribution on the position of the source of degradation and therefore to confirm whether or not the spots follow a complete spatial randomness (CSR) process. In order to simplify the mathematical treatment of the point-to-event distributions, the voltage probe was assumed to be located at one corner of the observation window which significantly reduces the number of cases to analyze. Infrared images revealed that the generation of the spots is associated with micro-explosions within the insulating material (HfO2) and with the local volatilization of the top metal electrode (Pt)

A comprehensive study of the short-circuit ruggedness of silicon carbide power MOSFETs

The behavior of Silicon Carbide Power MOSFETs under stressful short circuit conditions is investigated in this paper. Illustration of two different short-circuit failure phenomena for Silicon Carbide Power MOSFETs are thoroughly reported. Experimental evidences and TCAD electro-thermal simulations are exploited to describe and discriminate the failure sources. Physical causes are finally investigated and explained by means of properly calibrated numerical investigations, and are reported along with their effects on devices short-circuit capability

Transient out-of-SOA robustness of SiC power MOSFETs

Beyond their main function of high-frequency switches in modulated power converters, solid-state power devices are required in many application domains to also ensure robustness against a number of overload operational conditions. This paper considers the specific case of 1200 V SiC power MOSFETs and analyses their performance under three main transient regimes at the edge of and out of their Safe Operating Area: unclamped inductive switching led avalanche breakdown; short-circuit; operation as current limiting and regulating devices. The results presented highlight both inherent major strengths of SiC over Si and areas for improvement by tailored device design. The paper aims to contribute useful indications for technology development in future device generations to better match widespread and varied application requirements

A comprehensive study on the avalanche breakdown robustness of silicon carbide power MOSFETs

This paper presents an in-depth investigation into the avalanche breakdown robustness of commercial state-of-the-art silicon carbide (SiC) power MOSFETs comprising of functional as well as structural characterization and the corresponding underlying physical mechanisms responsible for device failure. One aspect of robustness for power MOSFETs is determined by its ability to withstand energy during avalanche breakdown. Avalanche energy (EAV) is an important figure of merit for all applications requiring load dumping and/or to benefit from snubber-less converter design. 2D TCAD electro-thermal simulations were performed to get important insight into the failure mechanism of SiC power MOSFETs during avalanche breakdow