The thermal stability of p-type CdTe crystals by using conductivity and Hall-effect measurements have been studied at room and slightly increased temperatures. It was observed that thermal changes often implicate an anomalous behavior of the hole density characterized by reversible decrease/increase in a heating/cooling regime. This anomaly was explained by a transfer of fast diffusing donors between Te inclusions and the bulk of the sample. Sodium and potassium were determined by the Secondary Ion Mass Spectroscopy (SIMS) as the most probable diffusing species. To verify this behavior samples were also treated in saturated NaCl solution for different time intervals in order to examine the influence of the oxide layer and sodium on the surface of the sample. To determine the structure of the surface the sample was characterized by ellipsometric and X-ray photoelectron spectroscopy (XPS) and SIMS. Very low determined diffusion coefficient of Na was explained by trapping of Na in Cd sublattice

Title: Diffusion of native defects and impurities in CdTe/CdZnTe. Author: Lukáš Šedivý Author's e-mail address: luky.sedivy@seznam.cz Department: Institute of Physics of Charles University Supervisor: Doc. Ing. Eduard Belas, CSc. Supervisor's e-mail address: belas@karlov.mff.cuni.cz Abstract: In this thesis, the influence of structural defects on the electrical and de- tection characteristics of CdTe material was investigated. The performed research fo- cused on the reduction of structural defects in the material by annealing in Cd or Te vapor, while preserving acceptable features for X-ray and γ-ray detection. The mate- rial was characterized by measurement of the electrical resistivity and concentration and mobility of free carriers. Tellurium and cadmium inclusions were studied using infrared microscope. The static and dynamic properties of defect structures at high temperatures and de- fined Cd pressures was investigated, as well, and chemical diffusion coeficients describing the dynamic properties of these defects were experimentally determined. Keywords: monocrystal CdTe, structural defects in semiconductors, annealing in Cd or Te, chemical diffusion coefficient, γ-ray detectors. 1