COHERENT-POTENTIAL-APPROXIMATION CALCULATION OF THE VALENCE BANDS OF THE QUATERNARY ALLOY INXGA1-XASYP1-Y

The empirical bond-orbital model and the coherent-potential approximation (CPA) are used to study the valence-band structures of the quaternary alloy InxGa1-xAsyP1-y in a manner similar to our previous work on the ternary III-V compound alloys. The densities of states and the self-energies are correlated with the bond-energy levels and their fluctuations. The concentration variation of the valence-band edge (at Γ15) obtained in CPA for the quaternaries matched to the lattice parameters of GaAs and InP are compared with the results from the virtual-crystal approximation. The valence band is shown to contribute significantly to the bowing of the band-gap energy of these alloys. © 1979 The American Physical Society.