A. Focsa

Formation of thin film polycrystalline silicon on ceramic substrates for photovoltaics

Here we review the different methods used to form thin film polycrystalline silicon films on some commercially available ceramic substrates, namely alumina and mullite. The chemical vapor deposition (CVD) process on bare ceramics, the CVD on glassy layer (CVD-OGL) process, and the aluminum-induced crystallization (AIC) technique are reported. The latter is based on the overall layer exchange of adjacent Si and Al films during the formation of amorphous to polycrystalline Si. The structural quality of the different layers are reported and compared. The direct deposition of silicon on ceramics by high temperature CVD results on thick polycrystalline silicon layers but with small (<5 /spl mu/m) and quite distributed grains. The CVD-OGL allows formation of larger grains but still limited up to 10-20 /spl mu/m in size so far. Finally, the aluminum-induced crystallization (AIC) method, followed by the vapour phase epitaxy leads to the formation of polysilicon films with grains sizes up to 70 /spl mu/m, depending on the temperature of the layers exchange. The electrical quality of such layers is investigated through the photovoltaic properties of solar cells prepared on the different used ceramics.