Spectroscopic ellipsometry measurements of Al Ga1−N in the energy range 3–25 eV

Wethkamp, T.; Wilmers, K.; Esser, N.; Richter, Wolfgang; Ambacher, O.; Angerer, H.; Jungk, G.; Johnson, Robert L.; Cardona, M.

doi:10.1016/s0040-6090(97)00990-5

Cited by 68 publications

(52 citation statements)

References 17 publications

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“…In contrast to Ref. [9] a small bowing is found here for the higher energetic critical points, too (b = 0.2 eV, 0.1 eV, and 0.5 eV for E 1 , E 2 , and E 3 , respectively). This is not a real contradiction, but it is attributed to the higher optical quality of the layers studied in the present work.…”

Section: Resultscontrasting

confidence: 99%

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Dielectric function and critical points of the band structure for AlGaN alloys

Buchheim

Goldhahn

Rakel³

et al. 2005

Physica Status Solidi (b)

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The ordinary complex dielectric function (DF) of Al x Ga 1-x N alloys with 0 ≤ x ≤ 0.53 is determined by fitting spectroscopic ellipsometry data from the infrared to the vacuum ultraviolet spectral region (0.74 eV ≤ E ≤ 9.8 eV). The dispersion of the real part of the DF below the band gap is found to be in excellent agreement with previously published data. The obtained band gap energies are verified by photoluminescence and photoreflectance spectroscopy. In the high-energy range, three critical points of the band structure are clearly resolved. By applying a third-derivative based DF line shape analysis, the corresponding transition energies are determined. Their compositional dependences can be described on the basis of small bowing parameters.

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Section: Resultscontrasting

confidence: 99%

“…The rather poor surface quality did not allow to extract the bulk-like DFs [9]. However, the studies provided preliminary results concerning the energy shift of the CPBS as a function of alloy composition.…”

Section: Introductionmentioning

confidence: 98%

Dielectric function and critical points of the band structure for AlGaN alloys

Buchheim

Goldhahn

Rakel³

et al. 2005

Physica Status Solidi (b)

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“…Surface optical probes have been developed as a very sensitive tool in means of monitoring, and thereby controlling the growth of semiconductor films [3][4][5][6][7][8]. In particular, spectroscopic ellipsometry has proven its ability to measure sub-nm thicknesses of roughness or overlayers on surfaces [4,5], while the widely applied reflectance anisotropy spectroscopy is specifically selective to surface signals in case of cubic materials [7].…”

Section: Introductionmentioning

confidence: 99%

In‐situ ellipsometry: Identification of surface terminations during GaN growth

Cobet

Schmidtling

Drago

et al. 2003

phys. stat. sol. (c)

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Spectroscopic ellipsometry (SE) is used to determine GaN surface termination during growth with metal-organic vapor phase epitaxy (MOVPE) by a correlation to well known results of plasma-assisted molecular beam epitaxy (PAMBE).The results manifest that in MOVPE under typical growth conditions the surface is not terminated by a Ga-bilayer as suggested for MBE. Moreover, it turns out that ellipsometry can be used to characterize the surface reconstruction in wurtzite GaN similar as reflectance anisotropy does for cubic III -V compounds. The optical spectra for the PAMBE reveal clear differences between growth under Ga-rich and N-rich conditions, which are attributed to the presence of a Ga-bilayer and various N-rich reconstructions on the surface [1].

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“…[1][2][3][4][5][6] In particular, spectroscopic ellipsometry has proven its ability to measure sub-nm thicknesses of roughness or overlayers on surfaces. 2,3 In case of cubic semiconductors their fourfold bulk symmetry permits the use of reflectance anisotropy spectroscopy measurements in which only the surface contributes to the measurement, 5 but such measurements are not applicable to the threefold-symmetric (0001) surface of GaN.…”

mentioning

confidence: 99%

“…Using SE one is not limited to any special bulk or surface symmetry for optical characterisation. In particular it is of interest to probe the surface structure and chemistry during GaN growth by metal-organic vapor phase epitaxy (MOVPE) 6 since the associated high pressures preclude in-situ observation by electron diffraction techniques.…”

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confidence: 99%

Surface termination during GaN growth by metalorganic vapor phase epitaxy determined by ellipsometry

Cobet

Schmidtling

Drago

et al. 2003

Journal of Applied Physics

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Spectroscopic ellipsometry (SE) is used in study GaN films during growth by metal-organic vapor phase epitaxy (MOVPE) and correlation to well known results of plasma-assisted molecular beam epitaxy (PAMBE). Results for the PAMBE reveal clear differences between growth under Ga-rich and N-rich conditions, which are attributed to the presence of a Ga-bilayer on the surface (also seen with low energy electron-diffraction) in the former case. Results for MOVPE surfaces during growth or for surfaces which are stabilized under N H 3 are very similar to the N-rich PAMBE result.It is concluded that under normal growth conditions in MOVPE the surface is not terminated by a Ga-bilayer.

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Spectroscopic ellipsometry measurements of Al Ga1−N in the energy range 3–25 eV

Cited by 68 publications

References 17 publications

Dielectric function and critical points of the band structure for AlGaN alloys

Dielectric function and critical points of the band structure for AlGaN alloys

In‐situ ellipsometry: Identification of surface terminations during GaN growth

Surface termination during GaN growth by metalorganic vapor phase epitaxy determined by ellipsometry

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