InN dielectric function from the midinfrared to the visible range

The dispersion of the dielectric function for wurtzite InN is analytically evaluated in the region near the fundamental energy gap. The real part of the dielectric function has a logarithmic singularity at the absorption edge. This results in the large contribution into the optical dielectric constant. For samples with degenerate carriers, the real part of the dielectric function is divergent at the absorption edge. The divergence is smeared with temperatures or relaxation rate. The imaginary part of the dielectric function has a plateau far away from the absorption onset.