Is the (Cd,Mn)Te crystal a prospective material for X-ray and γ-ray detectors?

Andrzej Mycielski 1,  Arnold Burger 2,  Małgorzata Sowińska 3,  Michael Groza 2,  P. Wojnar 1,  Andrzej J. Szadkowski 1,  Barbara Witkowska 1,  Wojciech Kaliszek 1,  Paul Siffert 4

1. Polish Academy of Sciences, Institute of Physics, al. Lotników 32/46, Warszawa 02-668, Poland
2. Fisk University, Department of Physics, Materials Science and Applications Group, 1000 17th Ave. N., Nashville, TN 37208-305, United States
3. EURORAD C.T.T., 23, Rue du Loess - BP 20, Strasbourg F-67037, France
4. European Materials Research Society - Headquarters, 23, Rue du Loess - BP 20, Strasbourg F-67037, France

Abstract

To answer the title question - the technology and properties of the (Cd,Mn)Te crystals will be discussed as compared with those of the more commonly used (Cd,Zn)Te crystals.
The composition homogeneity of the large single crystals of the ternary compound seems to be easier to achieve in the case of (Cd,Mn)Te because the segregation coefficient of Mn in CdTe is negligible whith respect to that (approx. 1.4) of Zn
Only 15% of MnTe has to be added to CdTe to reach the best for the detector application value of the energy gap (in the range 1.7 - 2.2 eV), while the necessary amount of ZnTe is over 30%! This is because the composition dependence of the CdTe energy gap is for Mn twice as strong as for Zn. Using a smaller amount of the second cation diminishes many alloying-related problems.
Dopant-free as grown (Cd,Mn)Te crystals are of p-type, which is related to the Cd vacancies acting as acceptors. The number of vacancies can be reduced by the post-growth annealing in the Cd vapours and the high (~ 1010 Ωcm ) resistivity, required for good detectors, can be obtained by doping with donors.
The technology of the (Cd,Mn)Te crystals, undoped and compensated in the very large range of concentrations, and Cd-annealing of the samples will be discussed. Characterization of the obtained crystals by the measurements of resistivity, photoluminescence and photoconductivity will be described. The behaviour of the preliminary detectors will be shown.

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Presentation: invited oral at NATO Advanced Research Workshop, by Andrzej Mycielski
See On-line Journal of NATO Advanced Research Workshop

Submitted: 2004-08-12 16:41
Revised:   2004-08-18 14:52
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