In this paper a methodology to develop SPICE-based models of complex magnetic devices is presented. The proposed methodology is based on a reluctance equivalent circuit (rEC), which allows the user to study both the m...
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In this paper a methodology to develop SPICE-based models of complex magnetic devices is presented. The proposed methodology is based on a reluctance equivalent circuit (rEC), which allows the user to study both the magnetic and electric behavior of the structure under any operating conditions. The different elements required to implement the reluctance model, namely, constant reluctances, variable reluctances and windings, are implemented using SPICE behavioral modeling. These elements can thus be used to build a complete model for any magnetic device. The modeling process is illustrated with a particular example for a variable inductor. Simulations and experimental results are presented and compared to evaluate the accuracy and usefulness of the proposed modeling procedure.
The effects of isoelectronic Al doping into epitaxial GaN films grown by metal organic chemical vapordeposition on sapphire substrates were investigated. It was found, based on the measured electron mobility and x-ra...
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The effects of isoelectronic Al doping into epitaxial GaN films grown by metal organic chemical vapordeposition on sapphire substrates were investigated. It was found, based on the measured electron mobility and x-ray analysis, that there is a limiting point of the incorporation of Al into GaN in improving the crystal quality. The electron mobility of the undoped GaN film was 178 cm(2)/V s and the value greatly increased to 524 cm(2)/V s by doping a small amount of Al (up to 0.45% in concentration) into the GaN layer. A further increase in the Al concentration resulted in a degradation of the electron mobility, which decreased to 138 cm(2)/V s when the Al concentration was 0.82%. The output power of a side view light emitting diode (LEd) with the Al-doped GaN layer was estimated to be 15.76 mW at a forward current of 20 mA, which improved by 19% compared to that of a conventional LEd. These results show that a small amount of Al incorporation into a GaN layer improves the electrical and optical properties of the layer, which are attributed to the reduction of Ga vacancy and associateddefects, such as dislocations.
To improve the external quantum efficiency, a vertical type InGaN LEd (VT-LEd) is fabricated on a sapphire substrate with a surface hemispherically-pattemed by laser lift-off (LLO) technique. As a result, the VT-LEds ...
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To improve the external quantum efficiency, a vertical type InGaN LEd (VT-LEd) is fabricated on a sapphire substrate with a surface hemispherically-pattemed by laser lift-off (LLO) technique. As a result, the VT-LEds with a concavely patterned surface revealed an enhanced luminous intensity by four times compared to the device with a planar surface. This improvement in the VT-LEd performances is explained to be attributed mainly to the increase in the escaping probability of photons due to the corrugated LEd surface. The use of metallic substrate prepared by nickel electroplating seems the other factor for the increase of luminous intensity by considering reduced current crowding and better thermal conductivity. These devices are advantageous for high power operation.
To improve the external quantum efficiency, a vertical type InGaN LEd (VT-LEd) is fabricated on a sapphire substrate with a surface hemispherically-patterned by laser lift-off (LLO) technique. As a result, the VT-LEds...
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To improve the external quantum efficiency, high quality GaN film was grown on hemispherical patterned sapphire by controlling the V/III ratio during the initial growth stage. The luminous intensity of white flash lig...
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To improve the external quantum efficiency, high quality GaN film was grown on hemispherical patterned sapphire by controlling the V/III ratio during the initial growth stage. The luminous intensity of white flash light emitting diode (LEd) grown on hemispherical patterned sapphire (HPS) was estinated to be 5.8 cd at a forward current of 150 mA, which is improved by 20% more than that of LEd grown on conventional sapphire substrate. The improvement of luminous intensity was explained by considering not only an increase of the extraction efficiency via the suppressed total internal reflection at the corrugated interface but also a decrease of dislocation density. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
To improve the external quantum efficiency, high quality GaN film was grown on hemispherical patterned sapphire by controlling the V/III ratio during the initial growth stage. The luminous intensity of white flash lig...
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