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Imaginary parts of the dielectric function around the band gap at T = 10 K. The ordinary (blue) and extra-ordinary (red) dielectric functions are shown (open circles) together with a model line shape fit (dashed black line). For the extraordinary dielectric function, the single components adding up to are shown (red dashed curves). The black arrow marks the resonance energy of 6.032 eV. Please note that the peak maximum of at is at 17. The fit (dashed line) is chosen such to match the peak maximum.
Reflectivity calculated from the measured dielectric function (blue, continuous curve) in comparison to experimentally determined reflectivity (black, open circles). Remaining differences are mainly due to the better spectral resolution of the experiment implying the lamp. The imaginary part of the dielectric function is shown for comparison (red, this is the same spectrum as already shown in Fig. 1 ).
Comparison of and photoluminescence spectra under different polarization directions of the electric field vector. The scaling of the spectra is adjusted independently to make the free exciton region clearly visible. Bound exciton contributions are labelled by . Arrows mark the two free exciton bands at 6.032 and 6.040 eV.
Transition energies of the different free excitons measured for as a function of temperature. Open symbols represent peak energies from PL spectra, and filled red circles are results from fitting the dielectric function. The continuous red line is the best fit to the ellipsometric data using Pässler's equation. 23
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