OPTICAL FUNCTIONS FROM 0.02 TO 6 EV OF ALXGA1-XSB GASB EPITAXIAL LAYERS/

The complex refractive index (n) over tilde=n+ik and the dielectric fu nction <(epsilon)over tilde>=epsilon(1)+i epsilon(2) at room temperatu re of AlxGa1-xSb films with 0 less than or equal to x less than or equ al to 0.5, grown by molecular beam epitaxy on a GaSb substrate, were d etermined from 0.02 to 6 eV by using the complementary data from fast Fourier transform far-infrared, dispersive, and ellipsometric spectrom etry. The effect of the native oxide was accounted for and the self-co nsistency of the optical functions was checked in the framework of the Kramers-Kronig causality relations. In the restrahlen region the diel ectric function was well fitted by classical Lorentz oscillators; in t he transparent region below the fundamental gap E-0, the refractive in dex was modeled by a Sellmeier dispersion relation, and in the interba nd region the dielectric function near the critical points was analyze d through standard line shapes. Interpolating the fitting parameters o r the interband dielectric spectra, it was possible to obtain the opti cal functions for any concentration x between 0.0 and 0.5. (C) 1998 Am erican Institute of Physics. [S0021-8979(98)04720-3].