Deposition rate enhancement of cluster-free P-doped a-Si:H films using multi-hollow discharge plasma CVD method*

We have realized highly stable a-Si:H films of 4.7x10$^{15}$ cm$^{-3}$ in stabilized defect density at a high deposition rate of 3 nm/s using a multi-hollow discharge plasma CVD method by which incorporation of clusters into the films is drastically reduced [1]. To realize a-Si:H solar cells of a high efficiency, we have deposited cluster-free n-layer a-Si:H films by PH$_{3}$+SiH$_{4}$ multi-hollow discharge plasma CVD. The deposition rate sharply increased from 0.49 nm/s with increasing a gas flow rate ratio $R$= [PH$_{3}$]/[SiH$_{4}$] from 0 {\%} to 1.17 nm/s for $R$= 1.0 {\%}, then slightly increases to 1.27nm/s for $R $= 10{\%}. SiH emission intensity monotonically increases with $R$. A high surface reaction probability $\beta$ of 100{\%} for $R>$ 1{\%}, is estimated from the deposition rate. These results suggest the surface reaction rates of SiH$_{x}$ radicals are enhanced by PH$_{x}$ radicals. \\[4pt] [1] W. M. Nakamura, et al., Surface and Coating Technologies (2010) in press.