Modeling the Optical Constants of Al_xGa_1-xN Alloys

Abstract

We have modeled the dielectric function of wurtzite Al x Ga 1−x N alloys for normal polarization in the energy range up to 10 eV and for all compositions 0 ≤ x ≤ 1. The employed model takes into account one-electron contributions to the dielectric function at E 0 , E 1A , E 1B , and E 1C critical points, as well as excitonic contributions at those critical points. The model is very flexible, due to the use of adjustable broadening function instead of the conventional Lorentzian one. Model parameters are determined by acceptance-probability-controlled simulated annealing. We obtain excellent agreement with the experimental data for all available compositions.

Dielectric function and critical points of the band structure for AlGaN alloys

“…A linear increase between GaN and AlN was reported for both the E 1 and the E 2 transition energy. Finally, it should be noted that experimental data on ( ) E ε are the basis for adjusting the parameters used in analytical models in order to describe the DFs over an extended energy range [10]. It is worth noting that high-energy CPBS strongly influence the dispersion of 1 ε at lower energies which is one of the essential quantities for the design for example of Bragg reflectors.…”