A Step Toward High Temperature Intelligent Power Modules Using 1.5kV SiC-BJT

International audienceLooking back to the development of inverters using SiC switches, it appears that SiC devices do not behave like their silicon counterparts. Their ability to operate at high temperature makes them attractive. Developing drivers suitable for 200˚C operation is not straightforward. In a perspective of high integration and large power density, it is wise to consider a monolithic integration of the driver parts for the sake of reliability. Silicon is not suitable for high ambient temperature; silicon-on-insulator offers better performances and presents industrial perspectives. The paper focuses on a SiC BJT driver: it processes logical orders from outside, drives adequately the BJT to turn it either on or off, monitors the turn-off and turn-on state of the device, and acts accordingly to prevent failure. SiC BJT imposes specific performances different from the well known ones of SiC JFET or MOSFET. The paper addresses a preliminary analysis of a SOI driver, anticipating the behavior of SiC-BJT and the change in behavior at high temperature. A discret driver as been design and fabricated. Elementary functionnal blocks have been validated, and a BJT conveter successfully operated at high temperature with high efficiency (η = 88%)

Effects of the laser beam size on the Optical Beam Induced Current (OBIC) for the study of Wide Band Gap (WBG) Semi-Conductor Devices

International audienceUV Laser is used to generate electron-hole pairs into Wide Band-Gap (WBG) semiconductors (SiC, GaN or Ga2O3). In the space charge region, the electric field drives the collected carriers and a current, so-called Optical Beam induced Current (OBIC), can be measured. The induced current is then directly related to the electrical field in the device. The OBIC, is a non-destructive technique, which has been previously successfully used to characterize High Voltage (HV) SiC devices [1, 2, 3, 4]. In order to fully benefit of the advantages provided by WBG semiconductors materials and to avoid premature breakdown of the high voltage devices, it is mandatory to have efficient peripheral protections such as a MESA, a JTE and JTE rings…The OBIC characterization can help the technology computer-aided design (TCAD) and the device process to optimize the efficiency of the periphery protection by analyzing the electric field distribution in the structure and especially at the junction periphery. In this talk, we will present an in-house testbench called micro-OBIC which will allow us to characterize HV PiN diodes with a micro-meter spatial resolution

Near breakdown voltage optical beam induced current (OBIC) on 4H-SiC bipolar diode

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Stigma toward schizophrenia : do all psychiatrists behave the same? Latent profile analysis of a national sample of psychiatrists in Brazil

Background: An important issue concerning the worldwide fight against stigma is the evaluation of psychiatrists’ beliefs and attitudes toward schizophrenia and mental illness in general. However, there is as yet no consensus on this matter in the literature, and results vary according to the stigma dimension assessed and to the cultural background of the sample. The aim of this investigation was to search for profiles of stigmatizing beliefs related to schizophrenia in a national sample of psychiatrists in Brazil. Methods: A sample of 1414 psychiatrists were recruited from among those attending the 2009 Brazilian Congress of Psychiatry. A questionnaire was applied in face-to-face interviews. The questionnaire addressed four stigma dimensions, all in reference to individuals with schizophrenia: stereotypes, restrictions, perceived prejudice and social distance. Stigma item scores were included in latent profile analyses; the resulting profiles were entered into multinomial logistic regression models with sociodemographics, in order to identify significant correlates. Results: Three profiles were identified. The “no stigma” subjects (n = 337) characterized individuals with schizophrenia in a positive light, disagreed with restrictions, and displayed a low level of social distance. The “unobtrusive stigma” subjects (n = 471) were significantly younger and displayed the lowest level of social distance, although most of them agreed with involuntary admission and demonstrated a high level of perceived prejudice. The “great stigma” subjects (n = 606) negatively stereotyped individuals with schizophrenia, agreed with restrictions and scored the highest on the perceived prejudice and social distance dimensions. In comparison with the first two profiles, this last profile comprised a significantly larger number of individuals who were in frequent contact with a family member suffering from a psychiatric disorder, as well as comprising more individuals who had no such family member. Conclusions: Our study not only provides additional data related to an under-researched area but also reveals that psychiatrists are a heterogeneous group regarding stigma toward schizophrenia. The presence of different stigma profiles should be evaluated in further studies; this could enable anti-stigma initiatives to be specifically designed to effectively target the stigmatizing group

Silicon Carbide Controlled Current Limiter, Current Limitation Strategies, Foreseen Applications and Benefits

International audienceThe expansion of electricity networks (distribution of energy, telecommunication), strongly contributed to increase the risks of appearance of defects, such as surge or overload. This multiplicity and complexity of electric networks, the need to have reliable systems favoured the development of serial protection devices. Fuse solution allows an efficient and total protection but requires to replace an element in case of failure. Therefore, other solutions have been investigated. Complex systems have been developed, all based on serial compensation, such as supra-conductor material, GTO MOV combination ... Indeed, because of the strong energy appearance during a short circuit, it is necessary to limit and to dissipate the energy of the short circuit, under high bias. This constraint leads to a feasibility study of a current limiter in 4H silicon carbide (4H-SiC). A VJFET structure was retained focusing on a nominal current of IN = 1 A and a nominal voltage of VN = 690 V. The device was optimised, taking into account SiC excellent physical properties. The VJFET was designed checking the trade-off between a low on-resistance value, high voltage capability and the highest gate transconductance value. A first batch of component was made, validating the bi-directional limitation function in both current and voltage mode, (VMAX = 970 V). The efficiency of the protection was validated, demonstrating the capacity of a component to react very quickly (t < 1 µs). Using such a device is very suitable in several applications (protection against short circuit, transient over current…) as it will allow to reduce transient phenomena and thus increase the efficiency and lifetime of the whole system

Stigma toward schizophrenia: do all psychiatrists behave the same? Latent profile analysis of a national sample of psychiatrists in Brazil

Background: An important issue concerning the worldwide fight against stigma is the evaluation of psychiatrists’ beliefs and attitudes toward schizophrenia and mental illness in general. However, there is as yet no consensus on this matter in the literature, and results vary according to the stigma dimension assessed and to the cultural background of the sample. The aim of this investigation was to search for profiles of stigmatizing beliefs related to schizophrenia in a national sample of psychiatrists in Brazil. Methods: A sample of 1414 psychiatrists were recruited from among those attending the 2009 Brazilian Congress of Psychiatry. A questionnaire was applied in face-to-face interviews. The questionnaire addressed four stigma dimensions, all in reference to individuals with schizophrenia: stereotypes, restrictions, perceived prejudice and social distance. Stigma item scores were included in latent profile analyses; the resulting profiles were entered into multinomial logistic regression models with sociodemographics, in order to identify significant correlates. Results: Three profiles were identified. The “no stigma” subjects (n = 337) characterized individuals with schizophrenia in a positive light, disagreed with restrictions, and displayed a low level of social distance. The “unobtrusive stigma” subjects (n = 471) were significantly younger and displayed the lowest level of social distance, although most of them agreed with involuntary admission and demonstrated a high level of perceived prejudice. The “great stigma” subjects (n = 606) negatively stereotyped individuals with schizophrenia, agreed with restrictions and scored the highest on the perceived prejudice and social distance dimensions. In comparison with the first two profiles, this last profile comprised a significantly larger number of individuals who were in frequent contact with a family member suffering from a psychiatric disorder, as well as comprising more individuals who had no such family member. Conclusions: Our study not only provides additional data related to an under-researched area but also reveals that psychiatrists are a heterogeneous group regarding stigma toward schizophrenia. The presence of different stigma profiles should be evaluated in further studies; this could enable anti-stigma initiatives to be specifically designed to effectively target the stigmatizing group.Fabio Lorea Lawson is employee of Janssen-Cilag Farmacêutida Ltda., which funded the study. The sponsor had no influence on the design of the study; on the collection, analysis and interpretation of data; on the writing of the manuscript; or on the decision to submit the manuscript for publication

Search for Flavor-Changing Neutral Current Interactions of the Top Quark and Higgs Boson in Final States with Two Photons in Proton-Proton Collisions at s\sqrt{s} =13 TeV

Proton-proton interactions resulting in final states with two photons are studied in a search for the signature of flavor-changing neutral current interactions of top quarks (t) and Higgs bosons (H). The analysis is based on data collected at a center-of-mass energy of 13 TeV with the CMS detector at the LHC, corresponding to an integrated luminosity of 137  fb−1. No significant excess above the background prediction is observed. Upper limits on the branching fractions (B) of the top quark decaying to a Higgs boson and an up (u) or charm (c) quark are derived through a binned fit to the diphoton invariant mass spectrum. The observed (expected) 95% confidence level upper limits are found to be 0.019% (0.031%) for B(t→Hu) and 0.073% (0.051%) for B(t→Hc). These are the strictest upper limits yet determined

Measurement of the inclusive tt production cross section in proton-proton collisions at sNN\sqrt{s_{NN}} = 5.02 TeV

The top quark pair production cross section is measured in proton-proton collisions at a center-of-mass energy of 5.02 TeV. The data were collected in a special LHC low-energy and low-intensity run in 2017, and correspond to an integrated luminosity of 302 pb−1. The measurement is performed using events with one electron and one muon of opposite charge, and at least two jets. The measured cross section is 60.7 ± 5.0 (stat) ± 2.8 (syst) ± 1.1 (lumi) pb. A combination with the result in the single lepton + jets channel, based on data collected in 2015 at the same center-of-mass energy and corresponding to an integrated luminosity of 27.4 pb−1, is then performed. The resulting measured value is 63.0 ± 4.1 (stat) ± 3.0 (syst+lumi) pb, in agreement with the standard model prediction of 66.8+2.9−3.1 pb