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J. Aderhold

Bio: J. Aderhold is an academic researcher from Leibniz University of Hanover. The author has contributed to research in topics: Molecular beam epitaxy & Photoluminescence. The author has an hindex of 11, co-authored 36 publications receiving 1926 citations.

Papers
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Journal ArticleDOI
TL;DR: In this article, the authors present the results of a joint study with the Ioffe Physico-Technical Institute, Russian Academy of Science, Polytekhnicheskaya 26, 194021 St. Petersburg, Russia and the Belarus Academy of Sciences, Brovki 17, 220072 Minsk, Belarus.
Abstract: (a) Ioffe Physico-Technical Institute, Russian Academy of Science, Polytekhnicheskaya 26, 194021 St. Petersburg, Russia (b) Institut für Festkörpertheorie and Theoretische Optik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, D-07743 Jena, Germany (c) Department of Electronics and Information Science, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan (d) Institute of Solid State and Semiconductor Physics, Belarus Academy of Sciences, Brovki 17, 220072 Minsk, Belarus (e) LfI, University of Hannover, Schneiderberg 32, D-30167 Hannover, Germany

942 citations

Journal ArticleDOI
TL;DR: In this article, a survey of optical absorption, photoluminescence and photomodulated reflectance spectra of single-crystalline hexagonal InN layers is presented.
Abstract: A survey of most recent studies of optical absorption, photoluminescence, photoluminescence excitation, and photomodulated reflectance spectra of single-crystalline hexagonal InN layers is presented. The samples studied were undoped n-type InN with electron concentrations between 6 × 10 18 and 4 × 10 19 cm -3 . It has been found that hexagonal InN is a narrow-gap semiconductor with a band gap of about 0.7 eV, which is much lower than the band gap cited in the literature. We also describe optical investigations of In-rich In x Ga 1-x N alloy layers (0.36 < x < 1) which have shown that the bowing parameter of b ∼ 2.5 eV allows one to reconcile our results and the literature data for the band gap of In x Ga 1-x N alloys over the entire composition region. Special attention is paid to the effects of post-growth treatment of InN crystals. It is shown that annealing in vacuum leads to a decrease in electron concentration and considerable homogenization of the optical characteristics of InN samples. At the same time, annealing in an oxygen atmosphere leads to formation of optically transparent alloys of InN-In 2 O 3 type, the band gap of which reaches approximately 2 eV at an oxygen concentration of about 20%. It is evident from photoluminescence spectra that the samples saturated partially by oxygen still contain fragments of InN of mesoscopic size.

288 citations

Journal ArticleDOI
TL;DR: In this article, first and second-order Raman scattering in hexagonal hexagonal alloys was studied and the dependences of frequencies of all Raman-allowed optical phonons versus Al content were traced in detail in the entire composition range.
Abstract: Studies of first- and second-order Raman scattering in hexagonal ${\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{N}$ alloys are reported. The dependences of frequencies of all Raman-allowed optical phonons versus Al content are traced in detail in the entire composition range. The one-mode behavior of LO phonons and the two-mode behavior of the other phonons is established. It is shown that the composition dependences of ${A}_{1}(\mathrm{TO}),$ ${A}_{1}(\mathrm{LO}),$ ${E}_{1}(\mathrm{LO}),$ and ${E}_{2}(\mathrm{low})$ phonon energies are convenient tools for the quantitative characterization of the Al content in ${\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{N}$ alloys. The energy position of the ${B}_{1}(\mathrm{high})$ silent mode is proposed. A narrow gap separating the dispersion regions of transverse and longitudinal optical phonons is revealed in the phonon density-of-state function. The composition dependence of the phonon line broadening is investigated experimentally and theoretically. It is shown that the broadening is due to elastic phonon scattering by the composition fluctuations. A theoretical approach is used where the statistical and dynamical aspects of the phonon scattering are treated separately. The type, size, and number of the fluctuations responsible for the phonon line broadening are estimated. The theory is qualitatively consistent with the observed composition dependences.

156 citations

Journal ArticleDOI
TL;DR: In this article, it was shown that InN thin films can be successfully grown using the metalorganic molecular beam epitaxy (MOMBE) method using a charge carrier concentration as low as 8.8×1018 cm−3.

95 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, the authors describe the state-of-the-art computational methodology for calculating the structure and energetics of point defects and impurities in semiconductors and pay particular attention to computational aspects which are unique to defects or impurities, such as how to deal with charge states and how to describe and interpret transition levels.
Abstract: First-principles calculations have evolved from mere aids in explaining and supporting experiments to powerful tools for predicting new materials and their properties. In the first part of this review we describe the state-of-the-art computational methodology for calculating the structure and energetics of point defects and impurities in semiconductors. We will pay particular attention to computational aspects which are unique to defects or impurities, such as how to deal with charge states and how to describe and interpret transition levels. In the second part of the review we will illustrate these capabilities with examples for defects and impurities in nitride semiconductors. Point defects have traditionally been considered to play a major role in wide-band-gap semiconductors, and first-principles calculations have been particularly helpful in elucidating the issues. Specifically, calculations have shown that the unintentional n-type conductivity that has often been observed in as-grown GaN cannot be a...

2,557 citations

Journal ArticleDOI
TL;DR: In this paper, a comprehensive and up-to-date compilation of band parameters for all of the nitrogen-containing III-V semiconductors that have been investigated to date is presented.
Abstract: We present a comprehensive and up-to-date compilation of band parameters for all of the nitrogen-containing III–V semiconductors that have been investigated to date. The two main classes are: (1) “conventional” nitrides (wurtzite and zinc-blende GaN, InN, and AlN, along with their alloys) and (2) “dilute” nitrides (zinc-blende ternaries and quaternaries in which a relatively small fraction of N is added to a host III–V material, e.g., GaAsN and GaInAsN). As in our more general review of III–V semiconductor band parameters [I. Vurgaftman et al., J. Appl. Phys. 89, 5815 (2001)], complete and consistent parameter sets are recommended on the basis of a thorough and critical review of the existing literature. We tabulate the direct and indirect energy gaps, spin-orbit and crystal-field splittings, alloy bowing parameters, electron and hole effective masses, deformation potentials, elastic constants, piezoelectric and spontaneous polarization coefficients, as well as heterostructure band offsets. Temperature an...

2,525 citations

Journal ArticleDOI
TL;DR: The optical properties of wurtzite-structured InN grown on sapphire substrates by molecular-beam epitaxy have been characterized by optical absorption, photoluminescence, and photomodulated reflectance techniques as discussed by the authors.
Abstract: The optical properties of wurtzite-structured InN grown on sapphire substrates by molecular-beam epitaxy have been characterized by optical absorption, photoluminescence, and photomodulated reflectance techniques. These three characterization techniques show an energy gap for InN between 0.7 and 0.8 eV, much lower than the commonly accepted value of 1.9 eV. The photoluminescence peak energy is found to be sensitive to the free-electron concentration of the sample. The peak energy exhibits very weak hydrostatic pressure dependence, and a small, anomalous blueshift with increasing temperature.

1,378 citations

Journal ArticleDOI
TL;DR: In this article, the authors present the results of a joint study with the Ioffe Physico-Technical Institute, Russian Academy of Science, Polytekhnicheskaya 26, 194021 St. Petersburg, Russia and the Belarus Academy of Sciences, Brovki 17, 220072 Minsk, Belarus.
Abstract: (a) Ioffe Physico-Technical Institute, Russian Academy of Science, Polytekhnicheskaya 26, 194021 St. Petersburg, Russia (b) Institut für Festkörpertheorie and Theoretische Optik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, D-07743 Jena, Germany (c) Department of Electronics and Information Science, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585, Japan (d) Institute of Solid State and Semiconductor Physics, Belarus Academy of Sciences, Brovki 17, 220072 Minsk, Belarus (e) LfI, University of Hannover, Schneiderberg 32, D-30167 Hannover, Germany

942 citations

Journal ArticleDOI
TL;DR: In this paper, the bandgap of InN was revised from 1.9 eV to a much narrower value of 0.64 eV, which is the smallest bandgap known to date.
Abstract: Wide-band-gap GaN and Ga-rich InGaN alloys, with energy gaps covering the blue and near-ultraviolet parts of the electromagnetic spectrum, are one group of the dominant materials for solid state lighting and lasing technologies and consequently, have been studied very well. Much less effort has been devoted to InN and In-rich InGaN alloys. A major breakthrough in 2002, stemming from much improved quality of InN films grown using molecular beam epitaxy, resulted in the bandgap of InN being revised from 1.9 eV to a much narrower value of 0.64 eV. This finding triggered a worldwide research thrust into the area of narrow-band-gap group-III nitrides. The low value of the InN bandgap provides a basis for a consistent description of the electronic structure of InGaN and InAlN alloys with all compositions. It extends the fundamental bandgap of the group III-nitride alloy system over a wider spectral region, ranging from the near infrared at ∼1.9 μm (0.64 eV for InN) to the ultraviolet at ∼0.36 μm (3.4 eV for GaN...

871 citations