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Very Wide-Gap and Device-Quality a-Si:H from Highly H2 Diluted SiH4 Plasma Decomposed by High RF Power

Published online by Cambridge University Press:  15 February 2011

N. Terada ,
S. Yata ,
A. Terakawa ,
S. Okamoto ,
K. Wakisaka  and
S. Kiyama
N. Terada
Affiliation:
New Materials Research Center, Sanyo Electric Co., Ltd. 1-1 Dainichi Higashimachi, Moriguchi, Osaka 570-8502, Japan
S. Yata
Affiliation:
New Materials Research Center, Sanyo Electric Co., Ltd. 1-1 Dainichi Higashimachi, Moriguchi, Osaka 570-8502, Japan
A. Terakawa
Affiliation:
New Materials Research Center, Sanyo Electric Co., Ltd. 1-1 Dainichi Higashimachi, Moriguchi, Osaka 570-8502, Japan
S. Okamoto
Affiliation:
New Materials Research Center, Sanyo Electric Co., Ltd. 1-1 Dainichi Higashimachi, Moriguchi, Osaka 570-8502, Japan
K. Wakisaka
Affiliation:
New Materials Research Center, Sanyo Electric Co., Ltd. 1-1 Dainichi Higashimachi, Moriguchi, Osaka 570-8502, Japan
S. Kiyama
Affiliation:
New Materials Research Center, Sanyo Electric Co., Ltd. 1-1 Dainichi Higashimachi, Moriguchi, Osaka 570-8502, Japan
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Abstract

The H2 dilution technique at a high deposition rate (RD) was investigated by depositing hydrogenated amorphous silicon (a-Si:H) under a high if power density of 750 mW/cm2, which is 20 times as large as that of conventional conditions. It was found that the H2 dilution ratio γ ( = [H2 gas flow rate] / [SiH4 gas flow rate]) tendency of the film properties, such as the H content (CH), optical gap (Eopt), SiH2/SiH and photoconductivity (σph) of a-Si:H is different for the high rf power (750 mW/cm2) and the medium rf power (75 mW/cm2) conditions. Under medium rf power, the CH, Eopt and SiH2/SiH decrease as γ increases. Under the high if power, on the contrary, the CH and Eopt, monotonously increase while maintaining a low SiH2/SiH and a high σph of 10-6 S/cm as γ increases. These results suggest that increasing the rf power enhances the H incorporation reactions due to H2 dilution. It is thought that a high rf power causes the depletion of SiH4 and hence the extinction of H radicals, expressed by SiH4 + H* → SiH3* + H2, is suppressed. A high H radical density enhances the incorporation of H into a-Si:H, resulting in very wide-gap a-Si:H with a high CH, Consequently, very wide-gap a-Si:H with device-quality (Eopt of 1.82 eV with an (αhv)1/3 plot, corresponding to > 2.1 eV with Tauc's plot, and σph of 10-6 S/cm) can be obtained at a high RD of 12 Å/s without carbon alloying.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 557: Symposium A – Amorphous and Heterogeneous Silicon Thin Films—Fundamentals to Devices—1999 , 1999 , 145
Copyright
Copyright © Materials Research Society 1999

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