Excitonic effects in the optical spectrum of GaAs

We present a calculation of the real (${\epsilon }_1$) and imaginary (${\epsilon }_2$) parts of the dielectric function of semiconductors at energies below and above the fundamental absorption edge. This model includes the $E_0$, $E_0$+${\Delta }_0$, $E_1$, $E_1$+${\Delta }_1$, and $E_2$($E_0^{\mathcal{’}}$) gaps as the main dispersion mechanisms. The model is also made to account for the excitonic effects at these critical points (CP’s). A model analysis indicates that the inclusion of the excitonic effects in our one-electron model corrects the strength of the peaks in the correct direction with experimental information (i.e., the $E_1$ peak becomes stronger and the $E_2$ peak weaker). Detailed analyses are presented for GaAs in the temperature range between 22–754 K, and results are in satisfactory agreement with the experimental data over the entire range of photon energies (0.0–6.0 eV). The temperature dependence of the strength and the broadening parameters at each CP are also given and discussed.