Hot wire CVD for epitaxial thickening of polycrystalline silicon seed layers made by AIC on glass

Large-grained polycrystalline silicon thin films on glass are attractive as the absorber layers for highly efficient, inexpensive, and stable solar cells that could replace the dominant silicon wafer-based technology. As an alternative to crystallization treatments of deposited amorphous silicon precursor layers, we are studying the approach of epitaxial thickening by hot wire CVD (at Utrecht University; UU) of large-grained polycrystalline seed layers produced by aluminium induced crystallization (AIC; at UNSW) at <500 °C on glass. We found that after the transfer of the AIC layers from Sydney to Utrecht, it is important to thoroughly clean them in order to achieve epitaxial thickening. At UU, the AIC layers were thickened by 150-300 nm, where poly2 conditions led to 60% crystalline ratio and epi conditions to 70% crystalline ratio. In both cases the optical (lateral) feature size was -5 μm, and epitaxial growth was observed to have taken place locally both in cross-sectional TEM and in optical micrographs. We report on preliminary solar cell structures made with AIC and HWCVD technology.