Al and Ga contributions to the density of states ofAlxGa1−xAs

The total valence-band density of states (DOS) and local Al s and Ga s contributions are calculated for ${\mathrm{Al}}_{\mathrm{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As by use of the coherent-potential approximation within an empirical tight-binding framework. In agreement with recent spectroscopic measurements, the central peak (near -7 eV) in the Al s local DOS sharpens continuously with increasing Al concentration, while the analogous peak in the total DOS broadens nonmonotonically. A similar continuous sharpening of the Ga s peak indicates a strong asymmetry between the substitution of Al in GaAs and Ga in AlAs.