Effective method for studying the effect of substitutional impurities on the band structure, in particular, semiconductor crystals are the optical measurements of the absorption edge and exciton reflection and photoluminescence spectra. In the case of the donor impurity a deformation of the energy bands and the formation of a so-called "tails" of the density of states takes place . This is quite well seen in the optical spectra (absorption edge is delayed and the exciton spectra are blurred). In the case of the formation of substitutional solid solutions the energy shift of the absorption edge and exciton bands take place .
Alloys such as Ga(As,P) or (Ga,In)(As,P) or more recently corresponding nitrides are widely used for light emitting diodes. The adjustment of emission wavelength is reached by band gap engineering resulting from substituting e.g. As by P (first example). See for instance Onton, Foster, J. Appl. Phys. 43 (1972) 5084.
See also paper devoted to Spectroscopic study of V doped Hg0.018Cd0.981Mn0.001Te bulk crystals as near-infrared materials for optical applications.
@Yu. Gnatenko, sir I am not able to open this document. Can you please paste link again
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