caa a22 4500 388114819 CHVBK 20180307125403.0 cr unu---uuuuu 161130s1999 xx s 000 0 eng 10.1557/S1092578300000673 doi S1092578300000673 pii (NATIONALLICENCE)cambridge-10.1557/S1092578300000673 Optical phonons and free-carrier effects in MOVPE grown AlxGa1−xN measured by Infrared Ellipsometry [Elektronische Daten] We report on the application of infrared spectroscopic ellipsometry (IR-SE) for wavenumbers from 333cm−1 to 1200cm−1 as a novel approach to non-destructive optical characterization of free-carrier and optical phonon properties of group III-nitride heterostructures. Undoped α-GaN, α-AlN, α-Al x Ga1−x N (x = 0.17, 0.28, 0.5), and n-type silicon (Si) doped α-GaN layers were grown by metal-organic vapor phase epitaxy (MOVPE) on c-plane sapphire (α-Al2O3). The four-parameter semi-quantum (FPSQ) dielectric lattice-dispersion model and the Drude model for free-carrier response are employed for analysis of the IR-SE data. Model calculations for the ordinary (∈ ⊥) and extraordinary (∈ ||) dielectric functions of the heterostructure components provide sensitivity to IR-active phonon frequencies and free-carrier parameters. We observe that the α-Al x Ga1−x N layers are unintentionally doped with a back ground free-carrier concentration of 1-4 1018cm−3. The ternary compounds reveal a two-mode behavior in ∈⊥, whereas a one-mode behavior is sufficient to explain the optical response for ∈||. We further provide a precise set of model parameters for calculation of the sapphire infrared dielectric functions which are prerequisites for analysis of infrared spectra of III-nitride heterostructures grown on α-Al2O3. Copyright © 1999 Materials Research Society AlGaN nationallicence n-type GaN nationallicence infrared nationallicence phonons nationallicence anisotropy nationallicence ellipsometry nationallicence free carriers nationallicence effective mass nationallicence Schubert M. Center for Microelectronic and Optical Materials Research and Department of Electrical Engineering, University of Nebraska-Lincoln Kasic A. Center for Microelectronic and Optical Materials Research and Department of Electrical Engineering, University of Nebraska-Lincoln Tiwald T.E. Center for Microelectronic and Optical Materials Research and Department of Electrical Engineering, University of Nebraska-Lincoln Off J. 4. Physikalisches Institut, Universität Stuttgart Kuhn B. 4. Physikalisches Institut, Universität Stuttgart Scholz Ferdinand 4. Physikalisches Institut, Universität Stuttgart MRS Internet Journal of Nitride Semiconductor Research Cambridge University Press 4/1(1999), e11 1092-5783 4:1<e11 1999 4 MIJ https://doi.org/10.1557/S1092578300000673 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1557/S1092578300000673 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Schubert M. Center for Microelectronic and Optical Materials Research and Department of Electrical Engineering, University of Nebraska-Lincoln NATIONALLICENCE 700 1- Kasic A. Center for Microelectronic and Optical Materials Research and Department of Electrical Engineering, University of Nebraska-Lincoln NATIONALLICENCE 700 1- Tiwald T.E. Center for Microelectronic and Optical Materials Research and Department of Electrical Engineering, University of Nebraska-Lincoln NATIONALLICENCE 700 1- Off J. 4. Physikalisches Institut, Universität Stuttgart NATIONALLICENCE 700 1- Kuhn B. 4. Physikalisches Institut, Universität Stuttgart NATIONALLICENCE 700 1- Scholz Ferdinand 4. Physikalisches Institut, Universität Stuttgart NATIONALLICENCE 773 0- MRS Internet Journal of Nitride Semiconductor Research Cambridge University Press 4/1(1999), e11 1092-5783 4:1<e11 1999 4 MIJ CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-cambridge