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Optical Constants, Critical Points, and Phonon Modes of GaAsN Single Layers

Published online by Cambridge University Press:  17 March 2011

G. Leibiger ,
V. Gottschalch ,
A. Kasik ,
B. Rheinländer ,
J. Šik  and
M. Schubert
G. Leibiger
Affiliation:
Faculty of Chemistry and Mineralogy, University Leipzig, Linnestrasse 3, 04103 Leipzig, Germany
V. Gottschalch
Affiliation:
Faculty of Chemistry and Mineralogy, University Leipzig, Linnestrasse 3, 04103 Leipzig, Germany
A. Kasik
Affiliation:
Faculty of Physics and Geoscience, University Leipzig, Linnestrasse 5, 04103 Leipzig, Germany
B. Rheinländer
Affiliation:
Faculty of Physics and Geoscience, University Leipzig, Linnestrasse 5, 04103 Leipzig, Germany
J. Šik
Affiliation:
Center for Microelectronic and Optical Materials Research, and Department of Electrical Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588
M. Schubert
Affiliation:
Center for Microelectronic and Optical Materials Research, and Department of Electrical Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588
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Abstract

Spectroscopic ellipsometry (SE) is employed to study the optical properties of GaAs1−yNy [0% ≤ y ≤ 3.7%] single layers for photon energies from 0.75 eV to 4.5 eV and for wavenumbers from 100 cm−1 to 600 cm−1. We provide parametric model functions for the dielectric function spectra of GaAsN in both photon energy ranges. The model functions for photon energies from 0.75 eV to 4.5 eV excellently match dielectric function data obtained from a numerical wavelength-by-wavelength inversion of the experimental data. Criticalpoint analysis of the ellipsometric data is performed in the spectral regions of the fundamental band gap and the critical points E1 and E1+δ1. The band-gap energy is red shifted whereas the E1 and E1+δ1 transition energies are blue shifted with increasing y. For y ≤ 1.65% the observed blue shift of the E1 energy is well explained by the sum of the effects of biaxial (001) strain and alloying. The GaAsN layers show two-mode behaviour in the infrared spectral range (100 cm−1 to 600 cm−1). We detect the transverse GaAs- and GaN- sublattice modes at wavenumbers of about 267 cm−1 and 470 cm−1, respectively. The polar strength of the GaN TO mode increases linearly with y. This effect can be used to monitor the nitrogen composition in GaAsN layers.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 639: Symposium G – GaN and Related Alloys-2000 , 2000 , G6.35
Copyright
Copyright © Materials Research Society 2001

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References

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