Optical dispersion relations in amorphous semiconductors InSb and GeSe2

The pseudodielectric-function spectra, ε(E)=ε1(E)+iε2(E), of amorphous (a-) InSb and GeSe2 semiconductors in the 1.5–5.5 eV photon-energy range at room temperature were measured by spectroscopic ellipsometry. The samples studied were prepared by radio frequency planar magnetron sputtering (a-InSb), and by the melt-quenching technique (a-GeSe2). The ε2(E) spectra for these semiconductors showed a single broad peak (a-InSb) and a double-peaked structure (a-GeSe2), respectively. The single broad peak found in a-InSb is typically observed in amorphous tetrahedral semiconductors. The double-peaked structure in the ε2(E) spectrum of a-GeSe2 closely resembles the a-Se and a-Te spectra and is described by a simple model consisting of two valence bands and a lower conduction band. The experimental ε2(E) spectra are analyzed using Jellison-Modine model [Appl. Phys. Lett. 69, 371 (1996)], and excellent agreement is achieved between the calculation and experiment over the entire range of photon energies. Dielectric-related optical constants, such as the complex refractive index, absorption coefficient, and normal-incidence reflectivity, of a-GeSe2 have also been presented.