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Discontinuity of the phonon mode frequency temperature dependence caused by a zero-gap state in HgCdTe alloys

Józef Cebulski 1Augusto Marcelli 1,2Eugen M. Sheregii 1M Piccinini 2

1. University of Rzeszow, Institute of Physics, Rejtana 16, Rzeszów 35-310, Poland
2. °Laboratori Nazionali Frascati INFN (INFN), Via E. Fermi 40, Frascati 00044, Italy


Quasi-binary alloy HgCdTe (MCT) form a continuous series of solid solutions of
Hg1-xCdxTe over x = 0 to 1 with zinc-blend crystalline structure1. In these alloys a band inversion and, as a result, a zero-gap state Eg ≡ G6 – G8 = 0 is realised as a composition varies from HgTe to CdTe. The zero-gap state depends on temperature too because there are several dependences Eg (x,T) for that is realised Eg = 0. These type of peculiarity can be realised by changing of Eg using press or temperature.

In this work are presented experimental results of optical reflectivity in far-infrared region (FIR) in wide interval of temperature (from 10 K to 290 K with step 10 K) for sample of Hg1-xCdxTe (x=0.115). For observation of effects described above a synchrotron radiation  FIR source has a great advantage as compared with the classical sources, intensity of which drops abruptly in this spectral region. Obtained results evidently show that frequencies of optical phonon modes have discontinuity in their temperature dependence when the zero-gap state takes place.

1.R. Dornhaus and G. Nimtz, Narrow Gap Semiconductors, Springer-Verlag, Berlin 1985,     v. 98, p. 159.


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Presentation: Poster at E-MRS Fall Meeting 2008, Symposium J, by Eugen M. Sheregii
See On-line Journal of E-MRS Fall Meeting 2008

Submitted: 2008-05-13 07:58
Revised:   2009-06-07 00:48