Recrystallized and epitaxially thickened poly-silicon layers on graphite substrates [solar cell manufacture]

Polycrystalline silicon films suitable for solar cell manufacturing have been realized by recrystallizing and epitaxially thickening thin silicon layers deposited on graphite substrates. The recrystallization is carried out in an electron beam zone melting process. Either vapor phase epitaxy or liquid phase epitaxy have been applied to enlarge the recrystallized seed layer to a thickness of 30-40 μm. This paper characterizes the seed layer and especially the epitaxial layer with regard to their structural properties. Surface morphology and crystalline quality have been analyzed for different process parameters. TEM investigations show how epitaxy is influenced by silicon carbide formed at the surface of the seed layer