A NEW FABRICATION METHOD FOR MULTICRYSTALLINE SILICON LAYERS ON GRAPHITE SUBSTRATES SUITED FOR LOW-COST THIN-FILM SOLAR-CELLS

A new method for the fabrication of a columnar, multicrystalline silic on layer on a graphite substrate is presented. This method basically i nvolves three process steps: (1) Deposition of a thin (3-5 mu m) silic on layer, (2) zone melting recrystallization of this layer with a line electron beam as the heat source to form a multicrystalline seed laye r, and (3) thickening of the seed layer by high temperature, epitaxial chemical vapour deposition (CVD) to a thickness of 20-40 mu m The rec rystallization leads to (110)[112]-textured silicon seed layers if suf ficiently high scan velocities are applied. The degree of deviation fr om the ideal (110)[112]-texture increases with decreasing scan velocit y. The doping level of the seed layer is found to be only weakly affec ted by the zone melting recrystallization. The epitaxial layer grown o n top of the seed layer exhibits a columnar grain structure.