Determination of the anisotropic dielectric function for wurtzite AlN and GaN by spectroscopic ellipsometry

The linear optical response of metastable α-Ga 2 O 3 is investigated by spectroscopic ellipsometry. We determine the ordinary dielectric function from lattice vibrations up to the vacuum ultraviolet spectral range at room temperature for a sample with a (0001) surface. Three out of four E u infrared-active phonon modes are unambiguously determined, and their frequencies are in good agreement with density functional theory calculations. The dispersion of the refractive index in the visible and ultraviolet part of the spectrum is determined. High-energy interband transitions are characterized up to 20 eV. By comparison with the optical response of α-Al 2 O 3 and with theoretical results, a tentative assignment of interband transitions is proposed.

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“…An analytical description of the point-by-point fitted ε 1,⊥ (hω) can be made using the model proposed by Shokhovets et al [64]:…”

Section: B Optical Properties In the Visible-to-ultraviolet Spectralmentioning

confidence: 99%

Ordinary dielectric function of corundumlike α−Ga2O3 from 40 meV to 20 eV

Feneberg

Nixdorf

Neumann

et al. 2018

Phys. Rev. Materials

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“…Because of the anisotropy of the energy position and amplitude of E 1 and E 1 (B), the dispersion of ε 1 in the visible range is anisotropic as well. It can be modeled by the empirical equation 35 …”

Section: B High-frequency and Static Dielectric Constantsmentioning

confidence: 99%

Anisotropic absorption and emission of bulk(11¯00)AlN

et al. 2013

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The intrinsic anisotropic optical properties of wurtzite AlN are investigated in absorption and emission. Full access to the anisotropy of the optical response of the hexagonal material is obtained by investigating the (1100) plane of a high-quality bulk crystal allowing electric field E polarization perpendicular (E ⊥ c) and parallel (E c) to the optical axis c. Spectroscopic ellipsometry yields the ordinary (ε ⊥ ) and extraordinary (ε ) dielectric functions (DFs) from 0.58 up to 20 eV. The comparison of the experimental data with recently calculated DFs demonstrates that Coulomb interaction has a strong impact not only on the spectral dependence around the fundamental absorption edge but also on the high-energy features usually discussed in terms of van Hove singularities. The fits of the second-order derivatives of ε and ε ⊥ provide the transition energies for the main features in this range. The DFs close to the fundamental absorption edge, dominated by free excitons, exciton-phonon complexes, and the exciton continuum, are independently confirmed by reflectivity and synchrotron-based photoluminescence excitation studies. Values for the band gaps, the crystal field ( cf = −221 ± 2 meV), and spin-orbit splittings ( so = 13 ± 2 meV) are obtained. Furthermore, we obtain accurate values for the static dielectric constants of ε S⊥ = 7.65 and ε S = 9.21, entering, e.g., the calculations of exciton binding energies. Photoluminescence is used to investigate the emission properties of the same sample.

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“…9 Ellipsometry results show unambiguously the absorption onset related with the C 9 valence band. 19 This transition is shown as a function of temperature in Fig. 6 for the Mg doped sample with x ¼ 0.733.…”

Section: B Valence Band Splittingmentioning

confidence: 99%

Optical properties of magnesium doped AlxGa1−xN (0.61 ≤ x ≤ 0.73)

Feneberg

Osterburg

Romero

et al. 2014

Journal of Applied Physics

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We investigate the optical properties of Al x Ga 1-x N:Mg with aluminum content of 0.61 x 0.733 in comparison to undoped and silicon doped reference samples. The ordinary dielectric functions, excitation, and emission spectra are reported at different temperatures. A comprehensive analysis yields quantitative data on the valence band structure of the ternary alloy, i.e., splitting and order of valence bands with different symmetries. Finally, the near band gap emission in AlGaN:Mg is found to be most probably dominated by donor to free-hole recombination. V C 2014 AIP Publishing LLC. [http://dx

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Determination of the anisotropic dielectric function for wurtzite AlN and GaN by spectroscopic ellipsometry

Cited by 104 publications

References 35 publications

Ordinary dielectric function of corundumlike α−Ga2O3 from 40 meV to 20 eV

Ordinary dielectric function of corundumlike α−Ga2O3 from 40 meV to 20 eV

Anisotropic absorption and emission of bulk(11¯00)AlN

Optical properties of magnesium doped AlxGa1−xN (0.61 ≤ x ≤ 0.73)

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