Dielectric tensor of monoclinic Ga<sub>2</sub>O<sub>3</sub> single crystals in the spectral range 0.5–8.5 eV

Sturm, Chris; Furthmüller, J.; Bechstedt, F.; Schmidt‐Grund, Rüdiger; Grundmann, Marius

doi:10.1063/1.4934705

Cited by 94 publications

(71 citation statements)

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“…Specifically, the optical properties of monoclinic β-Ga 2 O 3 were investigated in detail. Because of low crystal symmetry, phonon contributions [10,11] and interband transitions [11][12][13] are described by dielectric tensors containing four different nonzero tensor components. The Raman selection rules and tensor components are strongly influenced by the anisotropic properties of the material [14,15].…”

Section: Introductionmentioning

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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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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Section: Introductionmentioning

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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“…A thorough interpretation and understanding of ELNES and ELCE features requires insight from theory. The complexity of the excited-state spectra of TCOs [18][19][20] calls for an accurate first-principles description, that explicitly treats many-body effects. In this paper, we present a combined theoretical and experimental work investigating ELNES fingerprints of the local atomic environment in β-Ga 2 O 3 .…”

Section: Introductionmentioning

confidence: 99%

Atomic signatures of local environment from core-level spectroscopy inβ−Ga2O3

et al. 2016

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We present a joint theoretical and experimental study on core-level excitations from the oxygen K-edge of β-Ga 2 O 3 . A detailed analysis of the electronic structure reveals the importance of O-Ga hybridization effects in the conduction region. The spectrum from O 1s core electrons is dominated by excitonic effects, which overall red-shift the absorption onset by 0.5 eV, and significantly redistribute the intensity to lower energies. Analysis of the spectra obtained within many-body perturbation theory reveals atomic fingerprints of the inequivalent O atoms. From the comparison of energy-loss near-edge fine-structure (ELNES) spectra computed with respect to different crystal planes, with measurements recorded under the corresponding diffraction conditions, we show how the spectral contributions of specific O atoms can be enhanced while quenching others. These results suggest ELNES, combined with ab initio many-body theory, as a very powerful technique to characterize complex systems, with sensitivity to individual atomic species and to their local environment.

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“…For monoclinic gallia (β-Ga 2 O 3 ; a unit cell is depicted in Fig. 2 [11]) we evaluate the energy dependent complex dielectric tensor reported in [4]. We interpolate the experimental data (E) linearly and work here with energy steps of 0.01 eV.…”

Section: Application To Ga2o3mentioning

confidence: 99%

“…We focus on the optical axes in the absorption regime which starts at about 4.7 eV. The high energy cut-off of the data is limited by the spectral range of the ellipsometer used in [4]. (201) [100]…”

Section: Application To Ga2o3mentioning

confidence: 99%

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Singular optical axes in biaxial crystals and analysis of their spectral dispersion effects inβ−Ga2O3

Sturm

Grundmann

2016

Phys. Rev. A

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We classify and distinguish optically biaxial materials, which can have triclinic, monoclinic or orthorhombic crystal symmetry, by the degeneracy of the indices of refraction of their four singular optical axes (Windungsachsen) in the absorption regime. We provide explicit analytical solutions for angular orientations of the singular optical axes in monoclinic crystals and orthorhombic crystals.As a model material we analyze monoclinic gallia (β-Ga2O3) and discuss in detail the dispersion (i.e. the spectral variation of the angular position) of its singular optical axes. For a certain energy range (E ≈ 7.23-7.33 eV) we find quasi-uniaxial symmetry. At two energies (E ≈ 8.14 eV and E ≈ 8.37 eV) we find triaxial spectral points for which one regular optical axis and two singular optical axes exist. Concurrently a Stokes analysis of the spectral dependence of the electrical field eigenvectors is made and discussed for various crystal orientations. For a singular optical axis |S3| = 1; for the two degenerate singular axes at the triaxial point the Stokes vector is undefined. For a certain energy (E = 6.59 eV), the 010 -orientation is close to a singular optical axis, |S3| = 0.977. The analysis provided here is prototypical for the treatment of the optical properties of optically biaxial functional materials in the absorption and gain regimes.

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Dielectric tensor of monoclinic Ga₂O₃ single crystals in the spectral range 0.5–8.5 eV

Cited by 94 publications

References 50 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

Atomic signatures of local environment from core-level spectroscopy inβ−Ga2O3

Singular optical axes in biaxial crystals and analysis of their spectral dispersion effects inβ−Ga2O3

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Dielectric tensor of monoclinic Ga2O3 single crystals in the spectral range 0.5–8.5 eV

Cited by 94 publications

References 50 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

Atomic signatures of local environment from core-level spectroscopy inβ−Ga2O3

Singular optical axes in biaxial crystals and analysis of their spectral dispersion effects inβ−Ga2O3

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Product

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Dielectric tensor of monoclinic Ga₂O₃ single crystals in the spectral range 0.5–8.5 eV