Optical properties of In1−xGaxAsyP1−y alloys

Abstract

A method is described for the calculation of the real (${\epsilon }_1$) and imaginary (${\epsilon }_2$) parts of the dielectric function of ${\mathrm{In}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Ga}}_{\mathrm{x}}$ ${\mathrm{As}}_{\mathrm{y}}$ ${\mathrm{P}}_{1\mathrm{-}\mathrm{y}}$ quaternaries lattice matched to InP (0≤y≤1.0) at energies below and above the fundamental absorption edge. The present model is based on the Kramers-Kronig transformation and strongly connected with the electronic energy-band structure of the medium. This model reveals distinct structures at energies of the $E_0$, $E_0$+${\Delta }_0$, $E_1$, $E_1$+${\Delta }_1$, and $E_0^{\mathcal{’}}$ ($E_2$) critical points (CP’s). The indirect-band-gap transitions also play an important part in the spectral dependence of ${\epsilon }_2$. The calculated results are in satisfactory agreement with the experimental information over the entire range of photon energies (0–6.0 eV). The compositional dependence of the optical-transition strength and broadening parameters at each CP energy and indirect band gap is also given and discussed.