Optical properties of Al_xGa_(1-x)N alloy

摘要

The optical response of the Al_xGa_(1-x)N alloy has been analyzed using a simplified model of interband transitions (E≤10 eV). The present model reveals distinct structures at energies of the E_0, E_1,F_1], and E'_0 critical points. The Cauchy-Lorentz expression popularly used for the modeling of the three-dimensional M_0 and saddle-point excitonic transitions does not satisfy the Kramers-Kronig requirements but does so if its form is properly modified. As a result, excellent agreement is achieved between the experimental and calculated ε(E) spectra over the entire range of photon energies. Dielectric-related optical constants, such as the complex refractive index, absorption coefficient, and normal-incidence reflectivity, of the Al_xGa_(1-x)N alloy are also presented. The high-frequency and static dielectric constants of the Al_xGa_(1-x)N alloy are determined to be ε_∞(x) = 5.27-1.07x and ε_s(x) = 9.28-1.45x, respectively.