Hostname: page-component-586b7cd67f-dlnhk Total loading time: 0 Render date: 2024-11-28T21:07:31.502Z Has data issue: false hasContentIssue false
  • English
  • Français

Dielectric Functions of a-Si1-xGex:H versus Ge Content, Temperature, and Processing: Advances in Optical Function Parameterization

Published online by Cambridge University Press:  01 February 2011

Nikolas J. Podraza ,
Christopher R. Wronski ,
Mark W. Horn  and
Robert W. Collins
Nikolas J. Podraza
Affiliation:
[email protected], University of Toledo
Christopher R. Wronski
Affiliation:
[email protected], The Pennsylvania State University, Materials Research Institute, University Park, PA, 16802, United States
Mark W. Horn
Affiliation:
[email protected], The Pennsylvania State University, Materials Research Institute, University Park, PA, 16802, United States
Robert W. Collins
Affiliation:
[email protected], University of Toledo, Department of Physics and Astronomy, Toledo, OH, 43606, United States
Get access

Abstract

We have applied an advanced model to analyze the dielectric functions e = e1 + ie2 of amorphous silicon-germanium alloys (a-Si1-xGex:H) (i) as a function of alloy content × by varying the flow ratio G = [GeH4]/{[SiH4]+[GeH4]} in plasma-enhanced chemical vapor deposition (PECVD), and (ii) for the first time as a function of the measurement temperature Tm by cooling the newly-deposited film. All e spectra (1.5 − 4.5 eV) have been measured by spectroscopic ellipsometry (SE) either in real time during deposition or in situ post-deposition in order to avoid surface contamination. From the resulting extensive database, the optical properties of the alloys can be predicted for any value × and Tm within the ranges of the database. Such a capability is expected to be useful, for example, in real time control of optical gap in the PECVD process and in predicting the quantum efficiency of multijunction a-Si:H-based solar cells versus operating temperature. The effect on the database of other deposition parameters such as the electrode configuration and the H2-dilution ratio R = [H2]/{[SiH4]+ [GeH4]} have also been explored. The latter two studies provide useful insights into materials properties that can be extracted from a single spectroscopic measurement performed in real time during PECVD. For example, the energy width of the resonance in e correlates closely with the precursor surface diffusion characteristics observed throughout growth -- both determined from real time SE. This result indicates that short-range ordering in the film is improved when surface diffusion is promoted.

Keywords

photovoltaicSiGe
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 910: Symposium A – Amorphous and Polycrystalline Thin-Film Silicon Science and Technology – 2006 , 2006 , 0910-A10-01
Copyright
Copyright © Materials Research Society 2006

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

[1] Ferlauto, A.S., Ferreira, G.M., Pearce, J.M., Wronski, C.R., Collins, R.W., Deng, X., and Ganguly, G., J. Appl. Phys. 92, 2424 (2002).Google Scholar
[2] Collins, R.W., Ferlauto, A.S., Ferreira, G.M., Chen, C., Koh, J., Koval, R., Lee, Y., Pearce, J.M., and Wronski, C.R., Solar Energy Mater. Solar Cells 78, 143 (2003).Google Scholar
[3] Deng, X. and Schiff, E.A., in: Handbook of Photovoltaic Science and Engineering, edited by Luque, A. and Hegedus, S. (Wiley, New York, 2003), p. 505.Google Scholar
[4] Podraza, N.J., Ferreira, G.M., Wronski, C.R., and Collins, R.W., Mater. Res. Soc. Symp. Proc. 862, 43 (2005).Google Scholar
[5] Lautenschlager, P., Garriga, M., Viña, L., and Cardona, M., Phys. Rev. B 36, 4821 (1987).Google Scholar
[6] Cody, G.D., in: Semiconductors and Semimetals, Vol. 21B, edited by Pankove, J.I., Academic, New York (1984), p. 11.Google Scholar
[7] Dawson, R.M., Li, Y.M., Gunes, M., Heller, D., Nag, S., Collins, R.W., Wronski, C.R., Bennett, M., and Li, Y.-M., Mater. Res. Soc. Symp. Proc. 258, 595 (1992).Google Scholar
[8] Jellison, G.E. Jr, and Modine, F.A., Appl. Phys. Lett. 69, 371 (1996); 69, 2137 (1996).Google Scholar
[9] Price, J., Hung, P.Y., Rhoad, T., Foran, B., and Diebold, A.C., Appl. Phys. Lett. 85, 1701 (2004).Google Scholar