  The substitution of Mn in the III-V diluted magnetic semiconductors leads to
a strong electron scattering on impurities. Besides the features induced in the
valence band by the hybridization with the Mn d-states, also the conduction
band is affected by the absence of the Mn s-states at its edge. Also the high
concentration of compensating donors modifies the band structure. This is shown
on the absorption coefficient epsilon2(omega) of GaP doped with Mn and Se. The
absorption evaluated by ab initio density functional calculations starts with a
smooth tail and does not show the structure typical for III-V materials. We
analyze these features and the role of the donors on model systems using the
tight-binding coherent potential approach.
