The model dielectric function: Application to GaSb and InP

In this work we propose an analytical expression for the complex dielectric function which includes both discrete and continuum exciton effects. The model has been obtained by accurate introduction of Lorentzian broadening into Eliott's formula. Accurate introduction of broadening ensures that our model does not exhibit singularity at zero, which is present in the model proposed by Holden et al (T Holden, P Ram, F H Pollak, J L Freeouf, B X Yang and M C Tamargo 1997 Phys. Rev. B 56 4037). We have applied our model to the dielectric function data for GaSb and InP. Excellent agreement with the experimental data has been obtained for both materials. We show that agreement with the experimental data below the absorption edge can be further improved if the adjustable broadening modification is employed.