U. Haboeck

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.

The growth and optical properties of large, high-quality AlN single crystals

The effect of impurities and defects on the optical properties of AlN was investigated. High-quality AlN single crystals of more than 20mm2 size were examined. Different crucible materials and growth procedures were applied to the growth of bulk AlN by physical vapor transport method to vary the defect and the impurity concentrations. The crystalline orientation was investigated by Raman spectroscopy. Glow discharge mass spectrometry was used to determine the trace concentration of the incorporated impurities such as oxygen and carbon. The photoluminescence emission and absorption properties of the crystals revealed bands around 3.5 and 4.3eV at room temperature. Absorption edges ranging between 4.1 and 5.95eV were observed. Since no straight correlation of the oxygen concentration was obtained, a major contribution of oxygen or oxygen-related impurities was ruled out to generate the observed emission and absorption bands in the Ultraviolet spectral range. The carbon-related impurities and intrinsic defec...

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

Optical and structural microanalysis of GaN grown on SiN submonolayers

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Multifunctional III-nitride dilute magnetic semiconductor epilayers and nanostructures as a future platform for spintronic devices

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

Exchange instability of the two-dimensional electron gas in semiconductor quantum wells

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Photonic properties of ZnO epilayers

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

Coupling of intersubband charge-density excitations to longitudinal-optical phonons in modulation-doped GaAs quantum wells

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Inelastic Light Scattering by Elementary Excitations of the 2D Electron Gas at High Densities

and

Group I elements in ZnO

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