Avramenko K. Optical and structural-morphological properties of low-dimensional structures based on GaN and ZnO.

Thesis is devoted to the investigation of physical properties, phenomena and processes determining the vibrational and electronic properties of low-dimensional structures based on GaN and ZnO grown in different technological conditions. Scanning confocal Raman micro-spectroscopy was used to study spatial distribution of strains, structural quality and concentration (mobility) of free charge carriers in the growth direction of n++-n0-n++-GaN diode structures with submicron resolution. Quantitative methods for determination of the concentration and mobility of electrons in n-GaN layers based on theoretical analysis of plasmon-LO-phonon modes were developed. Resonance Raman micro-spectroscopy is shown to be a high efficiency method for investigation of compositional and strain distributions in ultrathin quantum layers of multilayer InGaN/GaN structures. The formation of spatially separated lateral compositional structure containing enriched indium InGaN nanoclusters is determined for epitaxial InxGa1-xN layer grown on sapphire substrate with GaN buffer layer. Dilute magnetic Zn1-хСoхO films (x = 5 and 15%) grown by molecular-beam epitaxy are shown to be ferromagnetic at room temperature and have column-like microstructure. Comprehensive optical studies established that Co2+ ions are in tetrahedral surrounding by oxygen ions, i.e. ions substitute Zn2+ in regular positions of wurtzite structure. Structural disorder effects in ZnO:N films grown by magnetron sputtering were investigated by micro-Raman spectroscopy. Registered Raman band at 275 cm-1 is interpreted as a local oscillation of zinc in tetrahedral surrounding where the nearest part of oxygen atoms replaced by nitrogen atoms.