Browsing by Author "Hoffmann Axel"

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Browsing by Author "Hoffmann Axel"

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  • Bound Excitons In Zno: Structural Defect Complexes Versus Shallow Impurity Centers 
    Wagner M; Callsen Gordon; Reparaz J S; Schulze J H; Kirste R; Cobet M; Ostapenko I A; Rodt S; Nenstiel C; Kaiser M; Hoffmann Axel; Rodina A; Phillips Matthew; Lautenschlager S; Eisermann S; Meyer Bruno (Amer Physical Soc, 2011)
    ZnO single crystals, epilayers, and nanostructures often exhibit a variety of narrow emission lines in the spectral range between 3.33 and 3.35 eV which are commonly attributed to deeply bound excitons (Y lines). In this ...
  • Dissociation of H-related defect complexes in Mg-doped GaN 
    Gelhausen Olaf; Phillips Matthew; Goldys Ewa; Paskova Tanja; Monemar Bo; Strassburg M; Hoffmann Axel (American Physical Society, 2004)
    Post-growth annealing and electron beam irradiation during cathodoluminescence were used to determine the chemical origin of the main optical emission lines in moderately and heavily Mg-doped GaN. The 3.27 eV donor-acceptor ...
  • Doping-level-dependent optical properties of GaN:Mn 
    Gelhausen Olaf; Malguth Enno; Phillips Matthew; Goldys Ewa; Strassburg M; Hoffmann Axel; Graf T; Gjukic M; Stutzmann M (American Institute of Physcis, 2004)
    The optical properties of molecular-beam-epitaxy-grown GaN with different Mn-doping levels (5–2331019 cm23) were studied by cathodoluminescence (CL) and optical transmission spectroscopy. Transmission measurements at 2 ...
  • Fe-centers in GaN as candidates for spintronics applications 
    Malguth Enno; Hoffmann Axel; Phillips Matthew; Gehlhoff W (Materials Research Society, 2006)
  • Fe in III-V and II-VI semiconductors 
    Malguth Enno; Hoffmann Axel; Phillips Matthew (Wiley - V C H Verlag GmbH & Co. KGaA, 2008)
  • Formation and dissociation of hydrogen-related defect centres in Mg-doped GaN 
    Gelhausen Olaf; Phillips Matthew; Goldys Ewa; Paskova Tanja; Monemar Bo; Strassburg M; Hoffmann Axel (Materials Research Society, 2004)
    Moderately and heavily Mg-doped GaN were studied by a combination of post-growth annealing processes and electron beam irradiation techniques during cathodoluminescence (CL) to elucidate the chemical origin of the ...
  • Identification of bound exciton complexes in ZnO 
    Strassburg M; Rodina A; Dworzak M; Haboeck Ute; Krestnikov Igor; Hoffmann Axel; Gelhausen Olaf; Phillips Matthew; Alves Helder; Zeuner Arndt; Hofmann Detlev; Meyer Bruno (Wiley-VCH Verlag GmbH, 2004)
    An identification of shallow bound exciton centers in ZnO is presented based on magneto-optical measurements and diffusion experiments. The thermalization behavior of the Zeeman split components confirms that the I4, I6, ...
  • Luminescence of InGaN MQWs grown on misorientated GaN substrates 
    Nenstiel C; Switaisky T; Alic M; Suski T; Albecht M; Phillips Matthew; Hoffmann Axel (IEEE, 2010)
    Optoelectronic devices based on InGaN have already been commercialised, however, the Indium content is limited to around 5%. With higher Indium concentration the quantum efficiency decreases, which is thought to be due to ...
  • Optical properties of Mn-doped GaN 
    Gelhausen Olaf; Malguth Enno; Phillips Matthew; Goldys Ewa; Strassburg M; Hoffmann Axel; Graf T; Gjukic M; Stutzmann M (Materials Research Society, 2004)
  • Phonon Deformation Potentials In Wurtzite Gan And Zno Determined By Uniaxial Pressure Dependent Raman Measurements 
    Callsen Gordon; Reparaz J S; Wagner M; Kirste R; Nenstiel C; Hoffmann Axel; Phillips Matthew (Amer Inst Physics, 2011)
    We report the phonon deformation potentials of wurtzite GaN and ZnO for all zone center optical phonon modes determined by Raman measurements as a function of uniaxial pressure. Despite all the structural and optical ...
  • Structural and electronic properties of Fe3+ and Fe2+ centers in GaN from optical and EPR experiments 
    Malguth Enno; Hoffmann Axel; Gehlhoff W; Gelhausen Olaf; Phillips Matthew; Xu X (American Physical Society, 2006)
    This work provides a consistent picture of the structural, optical, and electronic properties of Fe-doped GaN. A set of high-quality GaN crystals doped with Fe at concentrations ranging from 5 X 1017 cm-3 to 2 X 1020 ...
  • Structural and optical inhomogeneities of Fe doped GaN grown by hydride vapor phase epitaxy 
    Malguth Enno; Hoffmann Axel; Phillips Matthew (American Institute of Physics, 2008)
    We present the results of cathodoluminescence experiments on a set of Fe doped GaN samples with Fe concentrations of 5×1017, 1×1018, 1×1019, and 2×1020 cm-3. These specimens were grown by hydride vapor phase epitaxy with ...
  • Titanium-assisted growth of silica nanowires: from surface-matched to free-standing morphologies 
    Callsen Gordon; Reparaz J S; Wagner M; Vierck A.; Phillips Matthew; Thomsen C; Hoffmann Axel (IOP Publishing Ltd, 2011)
    We report on an oxide-assisted growth technique for silica nanowires which allows tuning the growth from surface-matched nanowires to free-standing morphologies based on growth control by Ti in the role of a catalyst and ...