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Author: Vadim Sirkeli Degree: doctor of physics and mathematics Speciality:  01.04.10 - Semiconductors physics and engineering Year: 2005 Scientific adviser: Dmitrii Nedeoglo doctor habilitat, professor, Moldova State University Institution:

Status The thesis was presented on the 21 September, 2005 Approved by NCAA on the 22 December, 2005 Abstract – 0.35 Mb / in romanian – 0.39 Mb / in russian

Keywords

Summary

The thesis is devoted to a complex study of electrical and luminescent properties of ZnSe single crystals doped with gold in the process of thermal treatment in Zn+Au or Se+Au melts with various concentration of dopant impurity.

For the first time on the grounds of electrical measurements, it is established that gold impurity shows amphoteric properties in n-ZnSe:Zn:Au crystals. At low Au concentration in Zn+Au melt (< 0.5 at %), gold atoms are preferentially introduced into interstitial sites of ZnSe crystal lattice and form electrically active Aui donors with activation energy of ED(Aui) = (22 ± 2) meV. For the first time, the dominating I -line (446.8 nm) is observed in the photoluminescence (PL) spectra for these samples, and it is formed by superposition of two PL lines attributed to native defectbound excitons (VSe) and impurity defect-bound excitons (Aui). Increasing doping level (Au concentration more than 1 at % in Zn+Au melt) results in the formation of acceptor-type simple AuZn substitutional defects and associative radiative centres (AuZn-Aui), (AuZn-DZn) and / or (VZn-Aui). It is shown that (AuZn-Aui) associative centres are responsible for the band of impurity luminescence (A-band) with a maximum at 458.2 nm in the PL spectra for n-ZnSe:Zn:Au crystals. As the doping level increases, the A-band intensity increases too, while the intensity of excitonic band decreases. Long-wave (599 nm and 628 nm) and infrared (878 nm) PL bands are ascribed to (AuZn-DZn) and (VZn-Aui) associative centres respectively. It is found that the gold-doping of ZnSe crystals from Se+Au melt leads to a preferential formation of acceptor-type AuZn impurity defects, which are responsible for the strong radiation in the blue spectral region (I -band at 447.2 nm).

On the grounds of investigation of Hall coefficient and electron mobility temperature dependencies in n-ZnSe:Zn:Au crystals, it is established that Au atoms incorporated into zinc sites of zinc selenide crystal lattice form simple single-charged electrically and optically active acceptor centres Au with electron configuration d10.

Oficial Reviewers

• Ion Tighineanu
  doctor habilitat, professor, Institute of Mathematics and Computer Science
• Leonid Culiuc
  doctor habilitat, professor, Institute of Applied Physics of the

 Theses