Joint Raman spectroscopy and HRXRD investigation of cubic gallium nitride layers grown on 3C-SiC

Rüsing, Michael; Wecker, T.; Berth, Gerhard; As, D. J.; Zrenner, A.

doi:10.1002/pssb.201552592

Cited by 4 publications

(5 citation statements)

References 47 publications

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“…Observable phonon mode branches and Raman tensor elements for backscattering configurations. For more details on the selection rules in these materials, the respective specialized papers should be referred[23,[36][37][38].…”

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confidence: 99%

Imaging of 180∘ ferroelectric domain walls in uniaxial ferroelectrics by confocal Raman spectroscopy: Unraveling the contrast mechanism

Rüsing

Neufeld

Brockmeier

et al. 2018

Phys. Rev. Materials

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In recent years, Raman spectroscopy has been used to visualize and analyze ferroelectric domain structures. The technique makes use of the fact that the intensity or frequency of certain phonons is strongly influenced by the presence of domain walls. Although the method is used frequently, the underlying mechanism responsible for the changes in the spectra is not fully understood. This inhibits deeper analysis of domain structures based on this method. Two different models have been proposed. However, neither model completely explains all observations. In this work, we have systematically investigated domain walls in different scattering geometries with Raman spectroscopy in the common ferroelectric materials used in integrated optics, i.e., KTiOPO 4 , LiNbO 3 , and LiTaO 3. Based on the two models, we can demonstrate that the observed contrast for domain walls is in fact based on two different effects. We can identify on the one hand microscopic changes at the domain wall, e.g., strain and electric fields, and on the other hand a macroscopic change of selection rules at the domain wall. While the macroscopic relaxation of selection rules can be explained by the directional dispersion of the phonons in agreement with previous propositions, the microscopic changes can be explained qualitatively in terms of a simplified atomistic model.

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confidence: 99%

Imaging of 180∘ ferroelectric domain walls in uniaxial ferroelectrics by confocal Raman spectroscopy: Unraveling the contrast mechanism

Rüsing

Neufeld

Brockmeier

et al. 2018

Phys. Rev. Materials

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“…Additionally, Raman measurements were performed to support the IRSE measurements. For quantitative comparison of the DFs and Raman spectra, we calculate the imaginary part of the dielectric loss function (ω) from pbp-DFs [74]: In the range ω < 1000 cm −1 , the Raman spectra are dominated by phonons from the substrates, namely the TO( ) Si at 521 cm −1 , the TO( ) 3C−SiC at 795 cm −1 , and the LO( ) Si at 972 cm −1 [75]. The TO( ) c−GaN phonon mode is forbidden and therefore not visible in these Raman spectra [76,77].…”

Section: Table II Characterization Results Of the Investigated Samplmentioning

confidence: 99%

Influence of the free-electron concentration on the optical properties of zincblende GaN up to 1×1020cm−3

Baron

Goldhahn

Deppe

et al. 2019

Phys. Rev. Materials

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We analyze the optical properties of zincblende gallium-nitride in the infrared and ultraviolet spectral range (≈27 meV-6.5 eV) experimentally by spectroscopic ellipsometry and provide a quantitative description of these results by k • p perturbation theory. Free-electron concentrations above 10 20 cm −3 are achieved by introducing germanium as a donor. We determine the dielectric function as well as band filling effects like the Burstein-Moss shift and band gap renormalization. The Kane model for the band structure of semiconductors near the-point allows to calculate the effective electron mass and to determine the nonparabolicity of the conduction band. At the same time, these results can be used to derive the free-electron concentration all-optically. The combination of Kane's model, Burstein-Moss shift, and band-gap renormalization can be used to expertly describe the measured transition energies up to ≈3.7 eV dependent on the carrier concentration, yielding an averaged hole mass of ≈0.61 m e for the contributing valence bands.

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“…It has been observed previously in TEM measurements that the density of SFs reduces with increasing epilayer thickness due to annihilation of SFs on different {111} crystal facets 12,23 . The model would therefore predict that the intensity of the HEB would reduce as the epilayer thickness is increased: this is an avenue which requires further investigation.…”

Section: Served Experimentallymentioning

confidence: 96%

“…However, growing phase-pure zb-GaN is challenging with epilayers often containing wz-GaN, as either stacking faults (SFs) or crystal inclusions, which has been reported to reduce the radiative efficiency of zb-GaN based QW structures 22 . The phase purity and structural quality of the zb-GaN can be assessed via Xray diffraction (XRD) [23][24][25][26] , Raman spectroscopy 23,24 and high-resolution transmission electron microscopy (HR-TEM) 16,27,28 . The presence of wz-GaN in zb-GaN epilayers has been seen to result in narrow peaks or a broad emission band in the low temperature photoluminescence (PL) spectrum at energies between the bandgaps of zb and wz-GaN [12][13][14]18,24,29 .…”

Section: Introductionmentioning

confidence: 99%

Effect of stacking faults on the photoluminescence spectrum of zincblende GaN

Church

Hammersley

Mitchell

et al. 2018

Journal of Applied Physics

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The photoluminescence spectra of a zincblende GaN epilayer grown via metal-organic chemical vapour deposition upon 3C-SiC/Si (001) substrates were investigated. Of particular interest was a broad emission band centered at 3.4 eV, with a FWHM of 200 meV, which extends above the bandgap of both zincblende and wurtzite GaN. Photoluminescence excitation measurements show that this band is associated with an absorption edge centered at 3.6 eV. Photoluminescence time decays for the band are monoexponential, with lifetimes that reduce from 0.67 ns to 0.15 ns as the recombination energy increases. TEM measurements show no evidence of wurtzite GaN inclusions which are typically used to explain emission in this energy range. However, dense stacking fault bunches are present in the epilayers. A model for the band alignment at the stacking faults was developed to explain this emission band, showing how both electrons and holes can be confined adjacent to stacking faults. Different stacking fault separations can change the carrier confinement energies sufficiently to explain the width of the emission band, and change the carrier wavefunction overlap to account for the variation in decay time.

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Joint Raman spectroscopy and HRXRD investigation of cubic gallium nitride layers grown on 3C-SiC

Cited by 4 publications

References 47 publications

Imaging of 180∘ ferroelectric domain walls in uniaxial ferroelectrics by confocal Raman spectroscopy: Unraveling the contrast mechanism

Imaging of 180∘ ferroelectric domain walls in uniaxial ferroelectrics by confocal Raman spectroscopy: Unraveling the contrast mechanism

Influence of the free-electron concentration on the optical properties of zincblende GaN up to 1×1020cm−3

Effect of stacking faults on the photoluminescence spectrum of zincblende GaN

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