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SUB-BANDGAP ABSORPTION SPECTROSCOPY AND MINORITY CARRIER TRANSPORT PROPERTIES OF HYDROGENATED MICROCRYSTALLINE SILICON THIN FILMS

M. Günes1,* , O. Göktas1, S. Okur1, N. Isık1, R. Carius2, J. Klomfass2, F. Finger2

Affiliation

  1. Department of Physics, Izmir Institute of Technology, Gülbahçe Kampus 35430 Urla-Izmir, Turkey
  2. Institut für Photovoltaik, Forschungszentrum Jülich, GmbH, 52425 Jülich, Germany

Abstract

Hydrogenated microcrystalline silicon thin films have been prepared using HW-CVD and VHF-PECVD techniques with different silane concentrations. The steady-state photoconductivity, dual beam photoconductivity, photothermal deflection spectroscopy and steady-state photocarrier grating (SSPG) methods have been used to investigate the optical and electronic properties of the films. Two different sub-bandgap absorption methods have been applied and analyzed to obtain a better insight into the electronic states involved. For some films, differences existed in the optical absorption spectra when the measurements were carried out through the film side and through the substrate side. In addition, for some films, fringe patterns remained on the spectrum after the calculation of the fringe free absorption spectrum, which indicates that structural inhomogeneities were present throughout the film. Finally, minority carrier diffusion lengths deduced from the SSPG measurements were investigated as a function of the crystalline volume fraction (Ic RS) obtained from Raman spectroscopy. The longest diffusion lengths and lowest sub-bandgap absorption coefficients were obtained for films deposited in the region of the transition to the amorphous growth..

Keywords

Hydrogenated microcrystalline silicon, Sub-bandgap absorption, Steady-state photocarrier grating, Dual beam photoconductivity.

Submitted at: Dec. 9, 2004
Accepted at: Jan. 26, 2005

Citation

M. Günes, O. Göktas, S. Okur, N. Isık, R. Carius, J. Klomfass, F. Finger, SUB-BANDGAP ABSORPTION SPECTROSCOPY AND MINORITY CARRIER TRANSPORT PROPERTIES OF HYDROGENATED MICROCRYSTALLINE SILICON THIN FILMS, Journal of Optoelectronics and Advanced Materials Vol. 7, Iss. 1, pp. 161-168 (2005)