Optical constants, critical points, free carrier effects, and phonon modes of GaAsN single layers and GaAsN/InAs/GaAs superlattices

G. Leibiger, V. Gottschalch, A. Kasik, B. Rheinländer, J. Ŝik, M. Schubert

Research output: Contribution to conferencePaper

1 Scopus citations

Abstract

Spectroscopic ellipsometry (SE) is employed to study the optical properties of tensile (compressive) strained GaAs1-yNy(InAs)/GaAs [0% ≤ y ≤ 3.3%] superlattices and 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. Critical-point analysis of the ellipsometric data is performed in the spectral regions of the fundamental band gap and the critical points E1 and E11. The band-gap energy is red shifted whereas the E1 and E11 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, but with different slopes for the GaAsN/GaAs and GaAsN/InAs/GaAs superlattices, respectively. This is due to the different strain states. This effect can be used to monitor strain or nitrogen composition in GaAsN layers. We further detect free carriers in the GaAsN sublayers of the GaAsN/GaAs superlattices. The absence of free carriers in the InAs/GaAsN sublayers goes along with an improved morphology, which is reflected by a decrease of all broadening parameters and by room-temperature photoluminescence emission.

Original languageEnglish (US)
Pages7-12
Number of pages6
DOIs
StatePublished - 2000
Event27th International Symposium on Compound Semiconductors - Monterey, CA, United States
Duration: Oct 2 2000Oct 5 2000

Other

Other27th International Symposium on Compound Semiconductors
CountryUnited States
CityMonterey, CA
Period10/2/0010/5/00

ASJC Scopus subject areas

  • Engineering(all)

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    Leibiger, G., Gottschalch, V., Kasik, A., Rheinländer, B., Ŝik, J., & Schubert, M. (2000). Optical constants, critical points, free carrier effects, and phonon modes of GaAsN single layers and GaAsN/InAs/GaAs superlattices. 7-12. Paper presented at 27th International Symposium on Compound Semiconductors, Monterey, CA, United States. https://doi.org/10.1109/iscs.2000.947120