Ebara Solar, Inc.

Ebara Corporation

Ruth A Garcia

Daniel L Meier

Hubert P Davis

Joyce A Jessup

Jalal Salami

The present invention provides a system and method for creating self-doping contacts to silicon devices in which the contact metal is coated with a layer of dopant and subjected to high temperature, thereby alloying the silver with the silicon and simultaneously doping the silicon substrate and forming a low-resistance ohmic contact to it. A self-doping negative contact may be formed from unalloyed silver which may be applied to the silicon substrate by either sputtering, screen printing a paste or evaporation. The silver is coated with a layer of dopant. Once applied, the silver, substrate and dopant are heated to a temperature above the Ag&mdash;Si eutectic temperature (but below the melting point of silicon). The silver liquefies more than a eutectic proportion of the silicon substrate. The temperature is then decreased towards the eutectic temperature. As the temperature is decreased, the molten silicon reforms through liquid-phase epitaxy and while so doing dopant atoms are incorporated into the re-grown silicon lattice. Once the temperature drops below the silver-silicon eutectic temperature the silicon which has not already been reincorporated into the substrate through epitaxial re-growth forms a solid-phase alloy with the silver. This alloy of silver and silicon is the final contact material, and is composed of eutectic proportions of silicon and silver. Under eutectic proportions there is significantly more silver than silicon in the final contact material, thereby insuring good electrical conductivity of the final contact material.

Method and apparatus for self-doping contacts to a semiconductor

The present invention provides a system for self-doping contacts to silicon devices in which the contact metal is coated with a layer of dopant and subjected to high temperature, thereby alloying the silver with the silicon and simultaneously doping the silicon substrate and forming a low-resistance ohmic contact to it. The silver is coated with a layer of dopant. Once applied, the silver, substrate and dopant are heated to a temperature above the Ag&mdash;Si eutectic temperature (but below the melting point of silicon). The silver liquefies more than a eutectic proportion of the silicon substrate. This alloy of silver and silicon is the final contact material, and is composed of eutectic proportions of silicon and silver. Under eutectic proportions there is significantly more silver than silicon in the final contact material, thereby insuring good electrical conductivity of the final contact material.

Apparatus for self-doping contacts to a semiconductor

Method for self-doping contacts to a semiconductor

A process for fabricating a solar cell is described. The process includes: (1) providing a base layer, (2) fabricating an emitter layer of p-type conductivity on a same side as the non-illuminated surface of the base layer to provide a strongly doped p-type emitter layer and a p-n junction between the n-type base layer and the p-type emitter layer. The base layer of the present invention has n-type conductivity and is defined by an illuminated surface and a non-illuminated surface. The illuminated surface has light energy impinging thereon when the solar cell is exposed to the light energy and the non-illuminated surface is opposite the illuminated surface.

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Irwin, PA, United States of America

Ruth A Garcia