Modeling the optical constants of AlxGa1-xN alloys

We have modeled the dielectric function of wurtzite AI(chi)Ga(1-chi)N alloy s for normal polarization in the energy range up to 10 eV and for all compo sitions 0 less than or equal to chi less than or equal to 1. The employed m odel takes into account one-electron contributions to the dielectric functi on at E-0, E-1A, E-1B, and E-1c critical points, as well as excitonic contr ibutions at those critical points. The model is very flexible due to the us e of adjustable broadening function instead of the conventional Lorentzian one. Model parameters are determined by acceptance-probability-controlled s imulated annealing. We obtain excellent agreement with the experimental dat a for all available compositions.