Shtan'ko O. The іnfluence of defects on change of properties of semi-insulsting undoped gallium arsenide single crystals in thermal processes

Thesis for candidate degree in physics and mathematical sciences by speciality 01.04.07 - solid state physics. This work present the experimental researchers of change in thermal processes of the volume and surface properties of semi-insulting undoped gallium arsenide single crystals with different deflexion from stoichiometry under own and admixtured defects of it's structure. It was established, the surface thermal stability SIU GaAs crystals gets worse with increasing of the arsenic vacancies maintenance and dislocation density. The thermal stability improvement due to condition of prolonged (over two hours) cooling of crystals. As result of thermal admixtures introduction into undoped gallium arsenide crystals there are shown that decrease of recombination activity of EL2 senters due to EL2 - Cu complex formation occurring in such case, when copper atom in complex occupy mainly the gallium vacancies. Except copper the cadmium and selenium atoms have influence on radiative recombination through EL2 centers too. It was established, that value of mechanical stresses in the region of unhomogeneous admixture atoms distribution due to vacancy composition of crystal in such case if admixture diffusion take place to gallium vacancies and do not depend from their composition in cause of the interstitial diffusion mechanism. Key words: gallium arsenide single crystals, annealing, point defects, admixture, dislocation, diffusion, electrophysical properties, mechanical stresses.