  One of the basic optoelectronic characteristics is the absorption of any
optoelectronic device or material. We present the characteristics of pure GaAs
and the deviation of ideal spectra. Due to crystal defects, vacancies,
impurities, etc., energy states exist in the semiconductor other than the
allowed bands (conduction and valence bands). In this research, the effect of
transitions between these states on absorption spectra and how the absorption
coefficients change with the density and location of those states are analyzed
numerically. Among the cases of 0.07 eV, 0.12 eV, and 0.17 eV with the density
of 2%, 5%, 10%, 20%, and 30%, the minimum deviation occurs for the states
located 0.07 eV below the conduction band and when the energy states have the
minimum density of 2% and the deviation increases for the cases of 0.12 eV and
0.17 eV with higher densities.
