StatusThe thesis was presented on the 31 March, 2010
Approved by NCAA on the 3 June, 2010
Abstract– 0.48 Mb / in romanian
– 0.52 Mb / in russian
The thesis is written in Russian and includes an introduction, five chapters, general conclusions and a list of cited papers. The thesis consists of 116 text pages, 58 figures, 8 tables and the list of cited papers includes 123 references. The obtained results were published in 12 scientific papers. Key words: zinc selenide, crystal growth, doping, nitrogen, natrium, photoluminescence, electroconductivity, impurity and intrinsic defects, exciton, exciton – impurity complex.
The thesis is related to the investigation of technological parameters on the structural perfectiveness and purity of ZnSe crystals grown by physical vapor transport. The electrical and luminescent properties of ZnSe doped with I, Al, N, H, Cl, Ca and Na have been investigated.
As it came from the elaboration of the technology of ZnSe single crystals' growth, the use of the steep temperature profile with a minimum in the region located between the seed and the bottom of the ampoule together with the temperature gradient less than 0.6°C/cm and a growth temperature of 980÷1060°С makes possible the growth of crystals up to 3 cm3 in volume. The grown crystals are free of subgrain boundaries and twins and the density of dislocations is 0÷30 mm-2. It has been established the nitrogen impurity introduction in Se sublattice results in formation of NSe acceptor centers, having 104±5 meV activation energy. The last ones are compensating the uncontrollable donor impurity in n-ZnSe single crystals and it modifies the probability of radiative recombination with uncontrollable impurities participation.
The Na impurity incorporation into Zn sublattice results in formation of NaZn, acceptor centers,
having 105±3 meV activation energy as well as formation of Nai, NaZnVSe şi NaiNaZn donor centers,
their activation energies being equal to 18±3 meV, 35±3 meV and 52±9 meV respectively. These
centers a determining the edge PL of ZnSe single crystals. The selenium excess in ZnSe doped with
Na during growth, stabilizes thermodynamically the NaZn nonequilibrium acceptor centers.