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Hydrogen Diffusion in Undoped and B-Doped a-Si1-xCx:H

Published online by Cambridge University Press:  16 February 2011

R. Shinar ,
J. Shinar ,
G. Subramania ,
H. Jia ,
S. Sankaranarayanan ,
M. Leonard  and
V. L. Dalai
R. Shinar
Affiliation:
Microelectronics Research Center, Iowa State University, AMes, Iowa 50011
J. Shinar
Affiliation:
Ames Laboratory - USDOE and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011
G. Subramania
Affiliation:
Ames Laboratory - USDOE and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011
H. Jia
Affiliation:
Ames Laboratory - USDOE and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011
S. Sankaranarayanan
Affiliation:
Ames Laboratory - USDOE and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011
M. Leonard
Affiliation:
Microelectronics Research Center, Iowa State University, AMes, Iowa 50011
V. L. Dalai
Affiliation:
Microelectronics Research Center, Iowa State University, AMes, Iowa 50011 Department of Electrical and Computer Engineering, Iowa State University, Ames, IA 50011
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Abstract

A deuterium secondary ion mass spectrometry (SIMS) study of hydrogen diffusion in undoped and boron-doped a-Si0.86C0.4:H deposited by an electron cyclotron resonance plasma is described. The undoped films deposited at 250°C clearly indicated deuterium-hydrogen interdiffusion at T ≥ 350°C. The dispersion parameter a of the power-law time dependent diffusion constant D = D00(ωt)−α decreased from ∼0.3 at T = 350 and 400°C to ∼0.1 at 450°C, and the activation energy for a diffusion length of 1000 Å was ∼1.0 eV. These results are discussed in relation to previous studies of a-Si:H. The diffusion in ∼0.2 and ∼0.6 at.% B-doped a-Si0.86C0.14:H sharply differs from that in B-doped a-Si:H, where an enhancement of up to ∼103 was previously observed. In doped a-Si0.86C0.14:H, the diffusion of most of the H atoms is strongly suppressed, but a small fraction undergoes fast diffusion. IR Measurements indicate that the B-doping reduces the bulk-like Si-H stretch vibration at ∼2000 cm1. Upon annealing, the Si-CHn and C-H wag modes at ∼780 and ∼1000 cm−1, resp., increase, while the 640 and ∼2000 cm1 Si-H wag and stretch modes, resp., weaken, indicating transfer of hydrogen from Si- to C-bonds, in which the H atoms are apparently deeply trapped. As in a-Si:H, the fast diffusion component is apparently due to carrier recombination-enhanced weak Si-Si bond breaking. The results suggest that B-doping also induces microvoids and enhances the rate of breaking of weak Si-C bonds, leading to enhanced trapping of H.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 336: Symposium A – Amorphous Silicon Technology - 1994 , 1994 , 317
Copyright
Copyright © Materials Research Society 1994

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References

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