Foreword

This work reports on the performances of ohmic contacts fabricated on highly p-type doped 4H-SiC epitaxial layer selectively grown by vapor-liquid-solid transport. Due to the very high doping level obtained, the contacts have an ohmic behavior even without any annealing process. Upon variation of annealing temperatures, it was shown that both 500 and 800 °C annealing temperature lead to a minimum value of the Specific Contact Resistance (SCR) down to 1.3×10−6 Ω⋅cm2. However, a large variation of the minimum SCR values has been observed (up to 4×10−4 Ω⋅cm2). Possible sources of this fluctuation have been also discussed in this paper

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%)

Influence of the Masking Material and Geometry on the 4H-SiC RIE Etched Surface State

International audienceThe roughness of etched SiC surfaces must be minimized to obtain surfaces with a smooth aspect, avoiding micromasking artifacts originating from re-deposited particles during the etching process. Four varieties of masks, Al, Ni, Si and C, were deposited on the SiC surface by photolithographic process. The C structures were formed by annealing conversion of patterned thick photoresist. On these surfaces, dry etching was performed with an SF6/O2 plasma produced in a Reactive-Ion-Etching (RIE) reactor. Although a better aspect of the surface is obtained with Ni in comparison with Al mask, micromasking could also occur even with Ni if the mask design was not enough spaced out. With C and Si masks, which produce fluorides species with negative boiling temperature, smooth etched surface was obtained without micromasking, even for tight masks covering up to 90% of the SiC surface

Chimpanzees, sorcery and contestation in a protected area in Guinea-Bissau

In Cantanhez National Park in Guinea-Bissau the construction of meaning made upon encounters with chimpanzees is associated with local social life. If a chimpanzee makes an unprovoked attack on a person, its actions are often understood as those of a sorcerer. Chimpanzees are involved in two parallel accusation discourses, one is played in intimate spheres of sociability where sorcerers harm their kin to benefit from secret alliances, and the other addresses a wider audience perceived to benefit from chimpanzees which are being protected at the expense of other humans. Both narratives represent local criticism against transgressions to calculations of redistribution and reciprocity

Conception, réalisation et caractérisation d\u27interrupteurs haute tension en carbure de silicium

Les composants à semi-conducteur en silicium connaissent des limites en terme de rapidité, température de travail et d\u27encombrement. Elles sont dues aux propriétés intrinsèques du matériau. Pour pallier ces limites, CEGELY conçoit, réalise et caractérise des composants de puissance en carbure de silicium depuis une dizaine d\u27années. Le travail effectué au cours de cette thèse repose sur la réalisation de démonstrateurs en SiC de type thyristor et JFET possédant une tenue en tension de 5kV. Une structure innovante d\u27un transistor JFET a été conçue et réalisée. Après caractérisation et afin de diminuer les difficultés rencontrées en technologie, une nouvelle conception de JFET est proposée. Des thyristors à électrodes non co-planaires ont été caractérisés. Ils ont montré une tenue en tension de 4 kV et une courant de 1,3 A sous 13 V. Parallèlement, une structure novatrice de thyristor à électrodes co-planaires a été développée et est en cours de fabrication

Mémoire épigraphique et historique sur les tombeaux des émirs Beni-Zeiyan et de Boabdil, dernier roi de Grenade, découverts à Tlemcen

"Extrait du Journal asiatique, janvier-février, 1876."Mode of access: Internet

Influence de la période de la houle sur la stabilité des digues à talus

Les formules usuelles de stabilité des digues ignorent, entre autres, l'influence de la période de la houle sur la tenue des carapaces, alors que le coefficient de stabilité de Hudson peut varier dans le rapport de 1 à 3, en raison de cette influence. Les études expérimentales décrites dans l'article ont confirmées le rôle de la période du point de vue qualitatif, à défaut d'avoir permis d'exprimer les lois générales correspondantes, en l'état actuel des recherches