Dielectric Functions and Critical Points of GaAsSb Alloys

Abstract

We report the pseudodielectric functions and the critical points of GaAsxSb1-x ternary alloy films. Data were obtained by performing spectroscopic ellipsometry on 1-mu m-thick films grown on (001) GaAs by using molecular beam epitaxy. Artifacts from surface contaminants, including oxide overlayers, were minimized by using in-situ chemical cleaning, leading to accurate representations of the bulk dielectric responses of these materials. We determined the energies of the E-1, E-1+Delta(1), E'(0), E'(0)+Delta'(0), E-2, E'(2), and E'(1) critical points from numerically calculated second energy derivatives, as well as their compositional dependences by using lineshape fitting.