Parameterized optical properties of InAlP alloys.

We report values of parametric-model (PM) parameters that can be used to obtain dielectric functions (refractive indices) from 1.5 to 6.0 eV for ${{\rm In}_x}{{\rm Al}_{1 - x}}{\rm P}$InAlP alloys of arbitrary compositions $x$x. Using reported pseudo-dielectric data for several In compositions, we extract their dielectric functions by multilayer calculations, then parameterize them with PM lineshapes that well describe the asymmetric nature of their critical point (CP) contributions. We follow the ${E_0}$E fundamental bandgap as a function of $x$x, and determine the composition of the indirect-to-direct crossover.