Far-infrared and Raman Spectroscopy of CdTe0.97Se0.03(In)

Nebojsa Romcevic 1Maja Romcevic 1Jelena Trajic 1Dusanka Stojanovic 1Zorica Lazarevic 1Branka Hadzic 1Andrzej Mycielski 2

1. Institute of Physics (IF), Pregrevica 118, Belgrade 11080, Serbia
2. Polish Academy of Sciences, Institute of Physics, al. Lotników 32/46, Warszawa 02-668, Poland

Abstract

Far-infrared reflectivity and Raman spectra of CdTe0.97Se0.03(In) single crystals were measured in 40-500cm-1 spectral range at 80 and 300K temperatures. Studied material had been produced with the Bridgman method at the Institute of Physics, Polish Academy of Science, Warsaw. The analysis of the far-infrared spectra was made by a fitting procedure based on the dielectric function which includes spacious distribution of free carrier influence on plasmon-phonon interaction. In undoped sample (CdTe0.97Se0.03) two optical mode frequencies (TO/LO pairs) at about 147/169 and 173/177 cm-1 were obtained. Plasmon-phonon interaction is weak.

            In doped sample concentration of free carriers increasing and plasmon-phonon interaction is stronger. In that case, like in some other II-VI semiconductors[1], with high free carrier concentration, a surface layer with a low concentration of free carriers (depleted region) could be formed. Then, from this surface layer we can clearly see phonons. While the light penetration depth is greater than the surface layer thickness, we see both, coupled and non-coupled modes of the mixed crystals in the reflection spectra. In the Raman spectra we did not registered any influence of doping. The excellent agreement between the experimental data and theoretical spectra supports this assumption.

[1] N. Romcevic, M. Romcevic, A. Golubovic, Le Van Khoi, A. Mycielski, D. Jovanovic, D. Stojanovic, S. Nikolic, S. Duric, Journal of Alloys and Compounds 397 (2005) 52-57.

 

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Presentation: Poster at E-MRS Fall Meeting 2009, Symposium C, by Nebojsa Romcevic
See On-line Journal of E-MRS Fall Meeting 2009

Submitted: 2009-05-08 14:41
Revised:   2009-06-07 00:48