Optical properties of Al x Ga 1 − x N alloy

The optical response of the Al x Ga 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−Krönig 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 x Ga 1 − x N alloy are also presented. The high-frequency and static dielectric constants of the Al x Ga 1 − x N alloy are determined to be ε ∞ ( x ) = 5.27 − 1.07 x and ε s ( x ) = 9.28 − 1.45 x , respectively.