A. Zeuner

Nitrogen-related local vibrational modes in ZnO:N

We study the influence of nitrogen, a potential acceptor in ZnO, on the lattice dynamics of ZnO. A series of samples grown by chemical vapor deposition (CVD) containing different nitrogen concentrations, as determined by secondary ion mass spectroscopy (SIMS), was investigated. 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, similar to the incorporation of the p-dopant magnesium and hydrogen in GaN during metalorganic CVD.

Shallow donors and acceptors in ZnO

In order to realize controlled p-type doping in ZnO the role of extrinsic and intrinsic donors has to be clarified. The extrinsic n-type dopants Al, Ga and In are commonly found in bulk ZnO crystals, but hydrogen also appears in relevant concentrations eventually controlling the residual n-type carrier concentrations in nominally undoped ZnO. The optical properties of excitonic recombinations in bulk, n-type ZnO are investigated by photoluminescence (PL). At liquid helium temperature the neutral donor–bound excitons dominate in the PL spectrum. Two electron satellite (TES) transitions of the donor–bound excitons allow us to determine the donor binding energies ranging from 46 to 73 meV. In the as-grown crystals a shallow donor with an activation energy of 30 meV controls the conductivity. Annealing annihilates this shallow donor which has a bound exciton recombination at 3.3628 eV. Correlated by magnetic resonance experiments we attribute this particular donor to hydrogen. These results are in line with the temperature-dependent Hall-effect measurements. The Al, Ga and In donor–bound exciton recombinations are identified based on doping and diffusion experiments, and using secondary ion mass spectroscopy. We report on the optical properties of the shallow nitrogen acceptor in ZnO incorporated by diffusion, by ion implantation and by in situ doping in epitaxial films.

Structural and optical properties of epitaxial and bulk ZnO

In this letter, we compare the properties of bulk and epitaxial ZnO. The ZnO thin films were grown on GaN templates and on ZnO single crystals by vapor phase deposition using Zn and NO2 as precursors. We use high-resolution x-ray diffraction to resolve the structural properties. The rocking curves of the bulk crystal are extremely broad caused by a mosaic structure of the substrate. The homoepitaxial ZnO film mimics the properties of the ZnO substrate whereas ZnO films on GaN templates showed superior rocking curve half width as small as 230 arcsec. The optical properties are investigated by temperature-dependent photoluminescence. Different donor and acceptor bound excitons can be distinguished for a half width of the recombination lines less than 1 meV. Free exciton emission is already detectable at liquid-He temperatures proofing the high quality of the epitaxial films.

Optical investigations on excitons bound to impurities and dislocations in ZnO

Abstract The optical properties of excitonic recombinations in bulk ZnO are investigated by photoluminescence (PL) measurements. At liquid helium temperature the neutral donor bound excitons are positioned at 3.364, 3.362 and 3.361 eV, the line at 3.364 eV dominates the PL spectra. Annealing of the crystals demonstrates that the 3.364 eV vanishes, it is most likely caused by the hydrogen related donor. Two-electron satellite transitions of the donor bound excitons allow to determine the donor binding energies to 43, 52 and 55 meV. These results are in line with the temperature dependent Hall effect measurements. In the as-grown crystals two donors with binding energies of 30 and 50 meV control the conductivity, whereas after annealing only one donor with a binding energy of about 50 meV is necessary to fit the data perfectly. In addition at 3.335 eV an excitonic recombination is observed, which supported by spatially resolved cathodoluminescence measurements, is attributed to excitons bound to structural defects.

Magneto-optical properties of bound excitons in ZnO

We present results of magneto-optical measurements and theoretical analysis of shallow bound exciton complexes in bulk ZnO. Polarization and angular dependencies of magnetophotoluminescence spectra at 5 T suggest that the upper valence band has

Group I elements in ZnO

{\ensuremath{\Gamma}}_{7}

Valence Band Ordering and Magneto-Optical Properties of Free and Bound Excitons in ZnO

symmetry. Nitrogen doping leads to the formation of an acceptor center that compensates shallow donors. This is confirmed by the observation of excitons bound to ionized donors in nitrogen doped ZnO. The strongest transition in the ZnO:N

Optical Properties of the Nitrogen Acceptor in Epitaxial ZnO

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Lithium and sodium acceptors in ZnO

transition) is associated with a donor bound exciton. This conclusion is based on its thermalization behavior in temperature-dependent magnetotransmission measurements and is supported by comparison of the thermalization properties of the

Identification of bound exciton complexes in ZnO

{I}_{9}