Dielectric functions of AlxGa1-xSb (0.00<=x<=0.39) alloys from 1.5 to 6.0 eV.

Room-temperature pseudodielectric function spectra 〈ε(ω)〉=〈ε1(ω)〉+i〈ε2(ω)〉 of AlxGa1-xSb (0.00<=x<=0.39) alloys were measured from 1.5 to 6.0 eV by spectroscopic ellipsometry. Effects of surface overlayers on the measured spectra have been minimized as far as possible by performing in situ chemical etching on samples immediately before the measurements rather than correcting the measured data mathematically for the presence of overlayers. Analysis of second energy derivatives numerically calculated from the measured data yielded the critical-point energies of the E1, E1+Δ1, E0′, E2, and E1′ interband transitions. Dependence of the critical-point energies on composition x is obtained. [ABSTRACT FROM AUTHOR]