Effects of cluster incorporation into hydrogenated amorphous silicon films in initial discharge phase on film stability

We studied the effects of incorporation of hydrogenated amorphous silicon (a-Si:H) nanoparticles (clusters) generated in the initial discharge phase on light induced degradation of a-Si:H films. The amount of clusters incorporated into the films in the initial discharge phase is 15 times larger than that in the steady state. To evaluate the effects of such initial cluster incorporation on stability of a-Si:H films, we fabricated a-Si:H Schottky cells with and without initial cluster incorporation using a multi-hollow discharge plasma chemical vapor deposition method with a shutter and compared cell stability against light exposure. The degradation ratio of the cell without initial cluster incorporation is less than 1% even after 100 hour light soaking of 2.7 suns. Our results show that suppressing initial cluster incorporation into a-Si:H films is a key to stable a-Si:H cells. Moreover, Si-H₂ bonds in films can be reduced down to 1/10 using a cluster eliminating filter.