Effect of hydrogen content on the crystalline quality of PECVD-deposited silicon for solar cells

The crystalline quality of plasma-enhanced CVD (PECVD) silicon films has been studied by Raman spectroscopy and photoluminescence. Depth distribution of hydrogen atoms in the films has been evaluated by the elastic recoil detection technique. In the PECVD amorphous Si films, the depth distribution of hydrogen atoms is uniform. The film which contains more hydrogen atoms is more amorphous. On the other hand, there are few hydrogen atoms (<1 at.%) except at the film/substrate interface in the polycrystalline films. In the recrystallization of amorphous Si films, it is deduced that the dehydrogenation process starts before the crystallization process. Dehydrogenation induces the redistribution of the Si atoms to make the films crystallize.