MSA  Vol.3 No.8 , August 2012
The High Energy Region of the Absorption Edge of a-Si:H, a Theoretical Study—III
ABSTRACT
In this paper we try to give a reasonable account for the origin of the experimental optical energy gap Eo of a-Si:H deduced from the plot due to Cody ( vs. E). Using a realistic model density of states diagram for a-Si:H and the constant dipole matrix element assumption, and a reasonable definition of the real optical energy gap EG, a new theoretical equation for ε2(E) was derived. The plot of the square root of this function as a function of the photon energy E for appropriate fitting parameters gives a straight line fit in the energy region of significance extrapolating to the energy axis at a value similar to the experimental optical gap but about 0.1 eV lower than the theoretical optical gap EG proposed in our paper. We conclude that the experimental optical gap Eo does not necessarily coincide with any optical transition threshold in the density of states diagram of a-Si:H.

Cite this paper
S. Al-Ani, A. Ibrahim and S. Al-Rawi, "The High Energy Region of the Absorption Edge of a-Si:H, a Theoretical Study—III," Materials Sciences and Applications, Vol. 3 No. 8, 2012, pp. 562-565. doi: 10.4236/msa.2012.38080.
References
[1]   S. K. J. Al-Ani, S. S. Al-Rawi and A. Ibrahim, “The High Region of the Absorption Edge of a-Si:H I, an Analytical Study,” World Renewable Energy Congress-IX Florence Italy, 2006.

[2]   S. K. J. Al-Ani, A. Ibrahim and S. S. Al-Rawi, “The High Region of the Absorption Edge of a-Si:H II, Derivative Methods Analysis,” World Energy Congress-X and Exhibition (WRECX), 2008.

[3]   W. B. Jackson, S. M. Kelso, C. C. Tsai, J. W. Allen and S.-J. Oh, “Energy Dependence of the Optical Matrix Element in Hydrogenated Amorphous and Crystalline Silicon,” Physical Review B, Vol. 31, No. 8, 1985, pp. 5187-5198. doi:10.1103/PhysRevB.31.5187

[4]   G. D. Cody, “The Optical Absorption Edge of a-Si:H,” In: J. I. Pankove, Ed., Semiconductors and Semimetals, Academic Press, Waltham, 1984, p. 11.

[5]   J. Tauc, R. Grigorovici and A. Vancu, “Optical Properties and Electronic Structure of Amorphous Germanium,” Physica Status Solidi, Vol. 15, No. 2, 1966, pp. 627-637. doi:10.1002/pssb.19660150224

[6]   A. Ibrahim, “A Theortical Study of the High Absorption Region of the Optical Absorption Edge of Hydrogenated Amorphous Silicon (in Arabic),” Ph.D. Thesis, Baghdad University, Baghdad, 2002.

[7]   S. M. Malik and K. O’Leary, “Deviations from Square- Root Distributions of Electronic States in Hydrogenated Amorphous Silicon and Their Impact upon the Resultant Optical Properties,” Journal of Non-Crystalline Solids, Vol. 336, No. 1, 2004, pp. 64-70. doi:10.1016/j.jnoncrysol.2003.12.042

 
 
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