Low area metal contacts for photovoltaic devices

Abstract

In a method for forming a contact on semiconductor surface, a crystalline silicon surface is first oxidized, following which an aluminium layer is deposited onto the oxide layer. A layer of amorphous silicon is then deposited onto the aluminium layer. The structure is then heated to a temperature below the aluminium/silicon eutectic temperature to locally reduce the oxide layer in regions where the quality/density of the oxide layer is lower. Simultaneously, the amorphous silicon penetrates into the aluminium layer, in which it has a high mobility. With continued heating, the aluminium penetrates completely through the oxide layer in localized regions, exposing the crystalline silicon surface. The exposed silicon surface provides a sight for nucleating epitaxial growth, which occurs rapidly as silicon within the aluminium continuously feeds the solid phase epitaxial growth process. The rapid epitaxial growth facilitates the formation of a new crystalline silicon layer that occupies the original space where the oxide layer was grown. The epitaxially grown silicon provides a bridge between the original p-type silicon surface and the metal layer and is itself doped p-type such that the metal is in electrical contact with the original silicon surface via the epitaxially grown silicon in the localized regions where the oxide layer was reduced.