The optical response of egr;hyphen;GaSe for light polarization perpendicular to thechyphen;axis in the 2.0ndash;5.0hyphen;eV photonhyphen;energy range has been studied at room temperature by spectroscopic ellipsometry. The measured dielectrichyphen;function spectra reveal distinct structures at energies of theE1(sim;3.6 eV) andE3(sim;4.9 eV) critical points (CPs). The experimental data are analyzed on the basis of a simplified model of the interband transitions. TheE1structure is characterized by a twohyphen;dimensional (2D)M0CP plus 2D discrete exciton, and theE3structure is assumed to act as a damped harmonic oscillator. Results are in satisfactory agreement with the experiment over the entire range of photon energies.
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