There is rising interest in investigating the properties of ZnO epitaxial films due to its of superior properties such as high exciton binding energy combined with low lasing threshold density and good resistance to bombardment with high-energy particles. The material is a potential competitor for GaN-based light-emitting devices in the ultraviolet and blue spectral range. Like for other wide-band gap semiconductors as GaN and ZnSe controlled p-type doping is difficult. However, there have been reports on the synthesis of p-conducting ZnO doped with As and a Ga/N codoping as well as the fabrication of a p-n-junction by excimer-laser doping. Magnetic field dependent optical absorption and photoluminescence (PL) experiments were performed to study shallow bound exciton complexes in Na-, N-, Ga- and In- doped and nominally undoped ZnO. These data were interpreted using theoretical modeling calculations of the ordering of the valence bands, Zeeman splitting, selection rules for optical transitions and thermalization behavior for each of the investigated specimens. Both the angular-dependent magneto-PL results and the theoretical calculations indicate that the top of the valence band in ZnO possesses the Gamma7 symmetry. The sign and the value of the effective g factor of the holes involved in all bound exciton transitions were determined by analyzing the polarization properties and fitting the angular dependence of the transition energies. The incorporation of nitrogen into ZnO was studied by Raman-scattering experiments. The Raman spectra revealed vibrational modes at 275, 510, 582, 643 and 856 cm-1 in addition to the host phonons of ZnO. The intensity of these additional modes correlates linearly with the nitrogen concentration and can be used as a quantitative measure of nitrogen in ZnO. These modes are interpreted as local vibrational modes. Furthermore, SIMS showed a correlation between the concentration of incorporated nitrogen and unintentional hydrogen

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