Plasma and Fusion Research

Volume 14, 4406141 (2019)

Regular Articles

Identification and Suppression of Si-H2 Bond Formation at P/I Interface in a-Si:H Films Deposited by SiH4 Plasma CVD
Kazuma TANAKA, Hisayuki HARA, Shota NAGAISHI, Liu SHI, Daisuke YAMASHITA, Kunihiro KAMATAKI, Naho ITAGAKI, Kazunori KOGA and Masaharu SHIRATANI
Kyushu University, Fukuoka 819-0395, Japan
(Received 3 January 2019 / Accepted 21 April 2019 / Published 9 September 2019)

Abstract

Light-induced degradation is an important problem concerning hydrogenated amorphous silicon (a-Si:H) solar cells. A-Si:H films of lower Si-H2 bond density exhibit less light-induced degradation. In this study, Raman spectroscopy measurements of a-Si:H films with P-layer/I-layer structure reveal that high-density Si-H2 bonds exist in the I-layer within 60 nm of the P/I interface. These Si-H2 bonds originate from surface reactions of SiH3 radicals, as the alternative origin (i.e., cluster incorporation) is considerably suppressed by a multi-hollow discharge plasma chemical vapor deposition method. For an I-layer thickness of 20 nm, the density ratio of Si-H2 and Si-H bonds in the I-layer decreases from 0.133 to 0.053 as the substrate temperature increases from 170℃ to 250℃. Fine tuning of the substrate temperature during the initial stage of I-layer deposition is thus effective in suppressing Si-H2 bond formation at the P/I interface.

Keywords

plasma CVD, Si-H2 bond, a-Si:H, solar cell, Raman spectroscopy

DOI: 10.1585/pfr.14.4406141

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