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Influence of strain on the band gap energy of wurtzite InN
Author(s) -
Schley P.,
Goldhahn R.,
Gobsch G.,
Feneberg M.,
Thonke K.,
Wang X.,
Yoshikawa A.
Publication year - 2009
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.200880924
Subject(s) - wurtzite crystal structure , band gap , condensed matter physics , materials science , absorption edge , infrared , lattice constant , semiconductor , phonon , molecular physics , optoelectronics , chemistry , optics , physics , zinc , diffraction , metallurgy
Degenerate wurtzite InN films with electron concentrations in the range of 10 18 cm –3 were studied by using spectroscopic ellipsometry (SE) in two spectral ranges. The analysis of the frequencies of the coupled phonon‐plasmon modes in the mid‐infrared region allows the determination of the plasma frequency and thus of the carrier density in the bulk of the samples. SE from the near‐infrared to the visible range provides the dielectric function (DF) around the absorption edge. The electron concentration as an important input parameter enables accurate determination of Burstein–Moss shift and band‐gap renormalization for the analysis of the imaginary part of the DF. Taking into account the in‐plane strain of the films, which is caused by lattice mismatch between InN and buffer/substrate, we obtain a zero‐density strain‐free band gap of 0.675 eV at room temperature. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)