Hostname: page-component-586b7cd67f-2brh9 Total loading time: 0 Render date: 2024-11-29T07:33:36.778Z Has data issue: false hasContentIssue false
  • English
  • Français

Characterization of Monolayer-Level Composition and Optical Gap Profiles in Amorphous Silicon-Carbon Alloy Bandgap-Modulated Structures

Published online by Cambridge University Press:  15 February 2011

H. Fujiwara ,
Joohyun Koh ,
C. R. Wronski  and
R. W. Collins
H. Fujiwara
Affiliation:
Materials Research Laboratory, The Pennsylvania State University, University Park, PA 16802.
Joohyun Koh
Affiliation:
Materials Research Laboratory, The Pennsylvania State University, University Park, PA 16802.
C. R. Wronski
Affiliation:
Materials Research Laboratory, The Pennsylvania State University, University Park, PA 16802. Department of Electrical Engineering, andThe Pennsylvania State University, University Park, PA 16802.
R. W. Collins
Affiliation:
Materials Research Laboratory, The Pennsylvania State University, University Park, PA 16802. Department of Physics, The Pennsylvania State University, University Park, PA 16802.
Get access

Abstract

Over the past few years we have applied real time spectroscopie ellipsometry (RTSE) to characterize the structural, compositional, and optical gap profiles in continuously-graded amorphous silicon-carbon alloy films (a-Si1-xCx:H). Most recently, we have extended the RTSE methods to their monolayer sensitivity and resolution limits. In this study, continuous triangular variations in the carbon content × (0.02≤x≤0.24) within ∼25 to 130 Å thick graded layers were introduced at the i/p interfaces of the n-i-p solar cell structures using continuous variations in the flow ratio z=[CH4]/{[SiH4]+[CH4]} during rf plasma-enhanced chemical vapor deposition (PECVD). A virtual interface approximation has been applied to interpret the RTSE data collected during the growth of the graded interface layers. This analysis yields C-content depth-profiles with monolayer-level resolution and a compositional uncertainty of ±0.004. Even compositional gradients in which x changes by >0.2 within a few monolayers’ thickness are readily characterized. Lastly, a continuous increase in open circuit voltage with increasing graded interface layer thickness, saturating at ΔVoc=0.1 V after 100 Å, is observed in the n-i-p solar cells with graded layers. These results demonstrate the importance of the RTSE analysis in assessing bandgap engineered device designs.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 467: Symposium A – Amorphous and Microcrystalline Silicon Technology - 1997 , 1997 , 531
Copyright
Copyright © Materials Research Society 1997

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

REFERENCES

1. For a review, see Bernhard, N., Bauer, G. H., and Bloss, W. H., Prog. Photovoltaics Res. Appl. 3, 149 (1995).Google Scholar
2. Lim, K. S., Konagai, M., and Takahashi, K., J. Appl. Phys. 56, 538 (1984).Google Scholar
3. Schropp, R. E. I., Ouwens, J. D., von der Linden, M. B., van der Werf, C. H. M., van der Weg, W. F., and Alkemade, P. F. A., Mater. Res. Soc. Symp. Proc. 297, 797 (1993).Google Scholar
4. Kim, S., and Collins, R. W., Appl. Phys. Lett. 67, 3010 (1995).Google Scholar
5. Kim, S., Burnham, J. S., Koh, J., Jiao, L., Wronski, C. R., and Collins, R. W., J. Appl. Phys. 80, 2420 (1996).Google Scholar
6. Lu, Y., An, I., Gunes, M., Wakagi, M., Wronski, C. R., and Collins, R. W., Appl. Phys. Lett. 63, 2228 (1993).Google Scholar
7. Collins, R. W., Rev. Sci. Instrum. 61, 2029 (1990).Google Scholar
8. Aspnes, D. E., J. Opt. Soc. Am. A 10, 974 (1993).Google Scholar
9. Jellison, G. E. Jr, and Modine, F. A., Appl. Phys. Lett. 69, 371 (1996); 69, 2137 (1996).Google Scholar
10. Forouhi, A. R. and Bloomer, I., Phys. Rev. B 34, 7018 (1986).Google Scholar
11. Asano, A., Ichimura, T., Uchida, Y., and Sakai, H., J. Appl. Phys. 63, 2346 (1988).Google Scholar