Defects induced by oxygen and hydrogen in CdTe crystals

A Kisiel 3Andrzej Mycielski 2Jacek Polit 1E Sheregii 1J Cebulski 1M Piccinini 5Augusto Marcelli 5B V. Robouch 5M Cestelli Guidi 4,5A Nucara 4

1. University of Rzeszow, Institute of Physics, Rejtana 16, Rzeszów 35-310, Poland
2. Polish Academy of Sciences, Institute of Physics, al. Lotników 32/46, Warszawa 02-668, Poland
3. Jagiellonian University, Institute of Physics (IF UJ), Reymonta 4, Kraków 30-059, Poland
4. Dipartimento di Fisica and Unita' INFM, Universita' di Roma "La Sapienza", Piazzale Aldo Moro 2, Roma 00185, Italy
5. °Laboratori Nazionali Frascati INFN (INFN), Via E. Fermi 40, Frascati 00044, Italy

Abstract

Actually, an important parameter to evaluate the quality of CdTe crystals is the content of residual amount of oxygen in high purity crystals. As a consequence, pure Cd and Te (99,999%) are used to growth CdTe monocrystals and thin films that are then purified by heating in a reduced hydrogen atmosphere. In this purification process is necessary to keep a balance between O and H so that to characterize oxygen and hydrogen contributions we applied both medium infrared (MIR) and far infrared (FIR) reflection spectroscopy. The infrared analysis is a very powerful method to investigate defects and in particular may obtain information on defects created in CdTe monocrystals grown from Cd and Te components purified in a hydrogen atmosphere before crystallization.It is thus interesting to consider the problem of asserting the presence of defects in semiconductor binary compounds, by observing consequences induced by distortions of their elemental tetrahedra due to the presence of vacancies and of insite atoms within the tetrahedra or other intersticial presence.Our model thus considers the system A(VzxZ1-x) and (A1-yVay)Z as composed of five defect tetrahedron configurations: {zT-1,zT+1},T0,{aT-1 ,aT+1} where zT-1 , aT-1 tetrahedron with one vacancy, and zT1, aT1, with one interstitial are deformed tetrahedra.Detecting the five frequencies in presence would indicate the presence and amount of the defects being monitored.Reflectivity experiments were performed using a FTIR BRUKER Equinox 55 interferometer using both a standard Hg lamp and IR synchrotron radiation emitted by DAFNE the storage ring working at the INFN-LNF at Frascati.In the mid-infrared (500-3000 cm-1) region of these monocrystalline systems we observed the characteristic vibrational spectra of oxygen and hydrogen bounded to Cd and Te.Also a rich fine structure around the CdTe phonon frequency range in the far IR domain ,has been detected and analyzed.
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Presentation: oral at E-MRS Fall Meeting 2004, Symposium F, by Jacek Polit
See On-line Journal of E-MRS Fall Meeting 2004

Submitted: 2004-05-25 20:22
Revised:   2009-06-08 12:55
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