General Electric Company

Hsueh-Rong Chang

Bantval J Baliga

Charles S Korman

Tat-Sing P Chow

Robert Louis Steigerwald

Edward K Howell

Svante Prochazka

Joseph C Borowiec

Robert James Thomas

Khai D Ngo

John P Walden

David W Tong

Tah-Mun Su

Robert A Senecal

Sodium loss, free halide build-up, devitrification and wall etching of the arc chamber are substantially reduced in an electrodeless HID metal halide arc discharge lamp by a protective metal silicate coating present only on the interior, equatorial portion of the arc chamber wall which is closest to the arc plasma. Suitable coatings include a metal silicate of a metal selected from the group consisting essentially of scandium, yttrium, beryllium, rare earth metal and mixture thereof.

Protective metal silicate coating for electrodeless HID lamps

Silver metal and nickel silicide are added to the fill of an electrodeless high intensity metal halide discharge lamp, which includes at least one metal iodide as a fill ingredient, for controlling the iodine vapor level therein. The nickel silicide acts to getter oxygen which has been introduced into the arc tube during lamp processing, thereby avoiding oxidation of the metal iodide portion of the fill and a concomitant release of free iodine into the arc tube. The silver acts to getter free iodine available from the metal iodide(s) of the fill as metal diffuses into the quartz arc tube wall, forming silver iodide (AgI). The combination of silver and nickel silicide acts to control the iodine level below an arc instability threshold to promote and maintain arc stability. In addition, neither silver nor nickel silicide attack the quartz arc tube wall. Lamp performance and lamp life are thus substantially improved.

Use of silver and nickel silicide to control iodine level in

An amalgam is accurately placed and retained in an optimal location near the cold spot of an electrodeless SEF lamp for operation at a mercury vapor pressure in the optimum range from approximately four to seven millitorr. The amalgam is positioned at the tip of an extended exhaust tube near the apex of the lamp envelope by forming an indentation in the exhaust tube and, in some embodiments, a dose locating member in combination therewith. An evacuation hole is formed below the indentation for evacuation of the lamp envelope, or bulb, during lamp fabrication. In an alternative embodiment, the extension of the exhaust tube is situated perpendicular to the main portion of the tube to allow for lateral adjustment of the position of the amalgam, thereby allowing for even further control of the amalgam operating temperature.

Electrodeless fluorescent lamp with optimized amalgam positioning

An electrodeless SEF fluorescent discharge lamp of the type having an envelope with a re-entrant cavity formed therein for containing an excitation coil includes an amalgam positioned for maintaining an optimum mercury vapor pressure during lamp operation. The amalgam is doped with a magnetic material, such as iron, cobalt, nickel, aluminum or tungsten, and is initially located in an optimal operating position using a magnetic field generated by a magnet situated about the lamp envelope. Advantageously, the magnetic field can be used to relocate the amalgam within the exhaust tube, as desired, during lamp processing steps. After processing, the magnet is removed, and no amalgam holder is required.

Using a magnetic field to locate an amalgam in an electrodeless

A high intensity discharge lamp having a fill including at least one rare earth metal iodide has an additional metal component for avoiding a substantial loss of the metal component of the fill and the attendant substantial buildup of free iodine, thereby increasing the useful life of the lamp. During lamp operation, the additional metal component combines with iodine in the vapor phase, forming a relatively stable iodide and thus reducing the total level of free iodine in the lamp. As a result, arc instability is avoided. The additional metal component also emits visible light and hence improves efficacy. Moreover, the additional metal component does not attack the arc tube wall by reducing silica. Suitable additional metal components include indium and thallium.

Iodine getter for a high intensity metal halide discharge lamp

A coating for the arc tube of a high intensity metal halide discharge lamp includes at least two oxide layers for protecting the arc tube from devitrification, cracking and etching of the arc tube wall and for avoiding arc instability, thereby extending the useful life of the lamp. A first layer of the multi-layer oxide coating is applied directly to the arc tube to provide thermal compatibility in order to avoid cracking during lamp operation. At least one additional layer provides chemical stability of the arc tube wall with respect to the lamp fill. As a result, a substantial loss of the metal portion of the fill and a corresponding substantial buildup of free halogen are avoided, thereby avoiding devitrification and etching of the arc tube wall. Furthermore, for HID lamps including as a fill ingredient a metal, such as sodium, which diffuses into the arc tube wall and causes further devitrification thereof, at least one layer of the multi-layer oxide coating acts as metal-barrier.

Multi-layer oxide coating for high intensity metal halide discharge lamps

In-situ extraction of contaminants, such as PCBs, from soil is achieved by an electroosmosis technique. The soil is treated with a low concentration surfactant solution used as a purging liquid. The contaminant is dissolved in the ground water, aided by the purging liquid. An electric field is applied to a region of the soil causing the ground water, contaminant and surfactant to move by electroosmosis to a collection point where the purging liquid, dissolved contaminant and surfactant are collected and removed from the soil. This method may also be used to control the direction of seepage of the contaminants.

Surfactant augmented in-situ removal of PCBs from soil by electroosmosis

A semiconductor power switching device comprises a multicellular FET structure with a Schottky barrier diode structure interspersed therewith with at least some of the FET cells being free of Schottky barrier portions. The ratio of Schottky barrier contact area to FET cell area in the overall device may be adjusted to tailor the device for operation at specific current densities.

Multicellular FET having a Schottky diode merged therewith

A field controlled diode is provided with an insulated gate electrode for controlling the conductivity of the diode. The diode is turned off by applying a gate bias voltage which pinches off the drift region of the device to block current flow in the anode/cathode diode path. The turn-off characteristics of the device are enhanced by including transistor portions in the structure in which the drift region is not pinched off during turn-off to facilitate extraction of stored charge from the diode structure.

Field controlled diode (FCD) having MOS trench gates

A UMOS IGBT has a source electrode ohmic contact area which is at least 40% base region and preferably at least 50% base region in order to provide a high latching current and a large safe operating area.

Insulated gate bipolar transistor with improved latch-up current level

Improved trench gate field effect devices are provided by forming a thick oxide at the bottom of the trench. This thick oxide may be preferably formed by ion implantation into the bottom of the trench.

Trench gate structure with thick bottom oxide

A semiconductor power rectifier attains low forward voltage drop, low reverse leakage current and improved switching speed by utilizing Schottky contact regions in a p-i-n rectifier along with other means for reducing the required forward bias voltage. In a preferred embodiment, the other means for reducing the required forward bias voltage includes a respective trench between each respective pair of successively spaced current interruption means.

Power rectifier with trenches

A depletion mode thyristor includes a plurality of regenerative segments and a plurality of non-regenerative segments, each of which is elongated in a first direction. Regenerative and non-regenerative segments are interleaved in a second direction perpendicular to said first direction. A plurality of regenerative segments may be disposed between adjacent non-regenerative segments. Adjacent regenerative or non-regenerative segments are spaced apart by gate electrode segments which are effective, upon application of an appropriate bias voltage, for pinching off the regenerative segments to force the current therein to transfer to the non-regenerative segments to turn the device off. This structure enables large quantities of current to be transferred from regenerative segments to non-regenerative segments during turn-off without inducing detrimental current crowding.

Metal oxide semiconductor gated turn-off thyristor having an interleaved

An insulated field effect semiconductor device having source and drain regions extending to opposed surfaces of its semiconductor body is bidirectional and capable of blocking voltages in either of two opposing polarities and comprises a four terminal device having source and drain electrodes disposed on the opposed surfaces and a base electrode all ohmically connected to corresponding portions of the semiconductor body. An insulated gate is provided in a trench which extends into the semiconductor body for controlling the conductivity of a channel region extending within the base region between the source and drain regions. The device is free of source-to-base and drain-to-base short circuits. Control circuits enable this device to conduct or block both polarities of a high current AC voltage applied across its source and drain terminals while preventing undesired avalanche breakdown within the device.

Bidirectional field effect semiconductor device and circuit

A lateral depletion mode thyristor has both of its power electrodes and both of its emitter regions extending to the same surface of the semiconductor wafer. The device operates with both a regenerative current path and a non-regenerative current path. An insulated gate electrode structure is disposed in a trench and configured to pinch off the regenerative current path to force the current flowing therein to transfer to the non-regenerative current path, thereby interrupting the regenerative action within the device and causing it to turn off. In some embodiments, a second insulated gate electrode controls device turn-on.

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Scotia, NY, United States of America

Hsueh-Rong Chang