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Valence‐band splitting and optical anisotropy of AlN
Author(s) -
Rossbach G.,
Röppischer M.,
Schley P.,
Gobsch G.,
Werner C.,
Cobet C.,
Esser N.,
Dadgar A.,
Wieneke M.,
Krost A.,
Goldhahn R.
Publication year - 2010
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.200983677
Subject(s) - valence band , valence (chemistry) , anisotropy , materials science , optoelectronics , physics , band gap , optics , quantum mechanics
Abstract The dielectric function (DF) of hexagonal AlN on Si(111) is determined in the range between 1 and 9.8 eV by spectroscopic ellipsometry (SE). Due to its large negative crytal‐field splitting wurtzite AlN features large dichroism. Showing that SE is sensitive to both components of the DF around the absorption edge, a uniaxial model is applied which yields transition energies for the free excitonic state. The in‐plane tensile stress leads to a red‐shift of these transitions and to an enlarged splitting. The experimental data are compared to the results of band‐structure calculations demonstrating excellent overall agreement. In addition, two high‐energy critical points in the ordinary DF were determined at energies of about 7.75 and 8.85 eV.