Effects of discharge parameters on deposition rate of hydrogenated amorphous silicon for solar cells from pure SiH4 plasma

Abstract

A systematic deposition of hydrogenated amorphous silicon films from pure SiH₄ plasma was made in a capacitively coupled rf glow‐discharge system by changing anode–cathode spacing d and chamber pressure p simultaneously. The data of the deposition rate in the p‐vs‐d space had two boundaries. One was pd=const. The other seems to be pd²=const. The rf plasma can stably sustain between the boundaries. The boundaries are discussed with rf power per SiH₄ molecule and with overlapping Paschen’s lines of various fragments, especially H₂ due to the SiH₄ dissociation. We found the optimum conditions in which the deposition rate was more than 10 Å/s without large photo‐induced degradation. 10% efficient p‐i‐n solar cells were achieved with the intrinsic layer deposition rate of 3.9 Å/s and more than 6% efficiency with 10 Å/s.