Ground and neutral

In electrical engineering, ground and neutral are circuit conductors used in alternating current (AC) electrical systems. The ground circuit is connected to earth, and neutral circuit is usually connected to ground. As the neutral point of an electrical supply system is often connected to earth ground, ground and neutral are closely related. Under certain conditions, a conductor used to connect to a system neutral is also used for grounding (earthing) of equipment and structures. Current carried on a grounding conductor can result in objectionable or dangerous voltages appearing on equipment enclosures, so the installation of grounding conductors and neutral conductors is carefully defined in electrical regulations. Where a neutral conductor is used also to connect equipment enclosures to earth, care must be taken that the neutral conductor never rises to a high voltage with respect to local ground. Definitions Ground or earth in a mains (AC power) electrical wiring system

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Shallow donor and deep DX-like center in InAlN layers nearly lattice-matched to GaN

Jean-François Carlin, Nicolas Grandjean, Lorenzo Lugani, Marcel Py

Nonintentionally doped 200-nm-thick In0.16Al0.84N/n(+)-GaN samples were grown by metal-organic vapor phase epitaxy and used for the electrical characterization of InAlN. In the temperature range 180-400 K, the forward current of Schottky diodes is dominated by a tunneling mechanism below 1.2 V. Capacitance and conductance-temperature characteristics were measured at 1 MHz in the 90-400 K range and at various voltages. The conductance vs temperature reveals two peaks D-1 and D-2, which are attributed to bulk states in InAlN. Their characterization by admittance spectroscopy gives thermal activation energies of approximate to 68 meV and 290 meV, and thermal capture cross section of 9.7 x 10(-17) cm(2) and approximate to 6.2 x 10(-15) cm(2), respectively. The same levels are also revealed by extracting the temperature dependence of the carrier density in the neutral region of InAlN from I-V-T characteristics on the Schottky diode. A partial carrier freeze out is demonstrated and discussed in the framework of an existing theory for DX centers. The use of this approach is supported by the evidence of persistent photoconductivity effects, which strongly indicate the presence of DX centers in our material. It results that each donor in InAlN would exist in two distinct lattice configurations, a substitutional one (D-1, hydrogenic state) and a lattice-distorted one (D-2, DX state). From secondary ion mass spectrometry data, theoretical grounds, and previous experimental evidence in the AlxGa1-xN system, oxygen is the most probable candidate for such an unintentional dopant.

Amer Physical Soc2014

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Injection dependence of the electroluminescence spectra of phosphor free GaN-based white light emitting diodes

Nicolas Grandjean

Multicolor, multi-quantum well light emitting diodes have been fabricated by molecular beam epitaxy by inserting quantum wells of various widths in the active region. The In content of the wells is 15%-20% and the color is governed by carrier confinement and the Stark effect. Combining a proper number of blue and yellow quantum wells allows to obtain monolithic white LEDs. The electroluminescence spectra of the diodes have been studied. At low injection, the luminescence intensity varies quadratically with the injection current, showing that the electroluminescence originates from the depleted region of the diode, and that non-radiative recombination paths exist. However, for higher injection currents, the luminescence efficiency of the wells situated near the n-side of the junction starts to vary linearly with the current, and this is accompanied by the appearance of GaN electroluminescence. We show that this is due to the entering of these wells into the neutral region of the diode, explaining the injection dependence of the color of these multicolor LEDs.

2002

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MICRO-313: Actuators and Electromagnetic systems I

Le cours aborde les principales méthodes pour l'analyse de systèmes électromécaniques. Une étude des grandeurs physiques magnétiques est suivie par la conversion de l'énergie électrique en énergie mécanique. L'aimant permanent est étudié de manière macroscopique. L'aspect dynamique est vu à la fin.

MICRO-330: Sensors

Comprendre les principes physiques utilisés dans les capteurs. Vue générale des différents principes de transduction et de l'électronique associée. Montrer des exemples d'application.

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En électricité, la terre est un concept qui représente le sol (la masse terreuse, d'où son nom) en le considérant comme parfaitement conducteur et, par convention, au potentiel . Cette dernière hyp

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Une installation électrique est un ensemble cohérent de circuits électriques, d'appareillages électriques. Elle peut se situer dans un bâtiment ou un ensemble de bâtiments à usage d'habitation, indus