CARACTERISATION OPTIQUE ET ELECTRONIQUE DES SEMICONDUCTEURS AMORPHES PAR LA TECHNIQUE DE PHOTOCOURANT CONSTANTOptical and electronic characterization of amorphous semiconductors by means of constant photocurrent method in the continuous regime (DC-CPM)
We present in this article the optical and electronic properties of amorphous semiconductors in particular hydrogenated
amorphous silicon a-Si: H. Two samples, undoped and P-doped, are prepared by plasma enhanced chemical vapour deposition
(PECVD). The optical absorption coefficient of the two samples is measured by the constant photocurrent technique in
continuous mode (DC-CPM). Then the measured absorption spectra are converted into electronic density of states (DOS)
within the mobility gap. We have also developed a computer program to model DC-CPM by holding into account all the
possible thermal and optical transitions between the localized states in the gap and the extended states in the conduction and
valence band. The defect pool model for the electronic density of states (DOS) is incorporated in our modelling. Our
measurements show that the DC optical coefficient absorption is underestimated only for the undoped sample. Our modelling
showed us the importance to consider the two absorption coefficients due to the electrons and to the holes to reconstruct the
density of the occupied and non-occupied states within the gap mobility of the material.
Stat. Sol. (c) 1, No. 5, 1194-1207, 2004.
 V. Cech, and J. Stuchlik, Phys. Stat. Sol. (a) 187, No.
2, 487-491, 2001.
 W. B. Jackson, N. M. Amer, A. C. Boccara, and D.
Fournier,Applied Optics 20(8) (1981) 1333-1344.
 J. J. G. Van den Heuvel, M. Zeman and J. W.
Metselaar, Proceedings of the SAFE/IEEE
 M. Vanecek, J. Kocka, A. Poruba, and A. Fejfar, J.
Appl. Phys., 78, 6203, 1995.
 V. Karoutsos, K. Pomoni , A. Vomvas, and J.
Sotiropoulos, Phys. Stat. Sol. (b) 199, No. 127, 127-
7] C. Main, D. Nesheva, J. Optoelectronic and dvanced
Materials, Vol. 3, No. 3, 2001, p.653-664.
 T. Tibermacine, A. Merazga, Courrier du Savoir, No.
6, Juin 2005, pp.17-20.
 M. J. Powell and S. C. Deane, Phys. Rev. B 48, 10815
 M. J. Powell and S. C. Deane, Phys. Rev. B 53, 10121
 J. A. Schmidt and F. A. Rubinelli, J. Appl. Phys., 83
(1), 339 (1998).
 F. Siebke, H. Stiebig, A. Abo-Arais and H. Wagner,
Solar Energy Materials and Solar Cells 41/42 (1996),
 P. Jensen, Solid State Communications. Vol. 76, No.
11, pp. 1301-1303, 1990.
 A. Poruba and F. Schauer, Proceeding of the 8-th
Inter. School on Con. Matter Phys., Varna, Bulgaria,
19-23 September 1994.
 C.Main , S. Reynolds , I. Zrinscak and A. Merazga ,
2004 Journal of Non Crystalline Solids 338-340 228-
 P. Sladek and M. L. Theye, Solid State Comms.
Vol.89, No. 3, pp.199, 1994.
 I. Sakata, M. Yamanaka, S. Numase, and Y. Hayashi,
J. Appl. Phys. 71 (9), 4344-4353 (1992).
 G. Conte, F. Irrena, G. Nobile, and F. Palma, Journal
of Non-Crystalline Solids 164-166 (1993) 419-422.
 S. Lee, M. Günes, C. R. Wronski, N. Maley, M.
Bennett, Appl. Phys. Lett. 59 (13), 1578 (1991).
 J. Z. Liu, G. Lewen, J. P. Conde, and P. Roca i
Cabarrocas, Journal of Non-Crystalline Solids 164-
166 (1993) 383-386.