Dielectric function models for describing the optical properties of hexagonal GaN

Several different models have been employed for modeling the dielectric fun ction of hexagonal GaN in the range from 1 to 10 eV. Models are compared in terms of number of parameters required, intricacy of model equations, and possibility of accurate estimation of important physical parameters, such a s energies of critical points and exciton binding energies. Shortcomings an d advantages of each model are discussed in detail. Excellent agreement wit h the experimental data for GaN has been achieved with three of the investi gated models. It has also been shown that an assumption of adjustable broad ening instead of a purely Lorentzian one improves the agreement with the ex perimental data and enables elimination of excessive absorption below the g ap which is inherent to the models with Lorentzian broadening. (C) 2001 Ame rican Institute of Physics.