Effects of local atomic arrangements on the densities of phonon states ofGa1−xInxAs,Ga1−xInxSb,GaAs1−xSbx, andInAs1−xSbx

The densities of phonon states of ${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{In}}_{\mathrm{x}}$As, ${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{In}}_{\mathrm{x}}$Sb, ${\mathrm{GaAs}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Sb}}_{\mathrm{x}}$, and ${\mathrm{InAs}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Sb}}_{\mathrm{x}}$ are evaluated using the recursion method and the rigid-ion model with first- and second-nearest-neighbor force constants. Principal features of the density-of-states spectra are associated with vibrations of various local atomic arrangements in the alloys. The observed ‘‘one+two-mode behavior’’ of these alloys is attributed to the degeneracy of the long-wavelength optic phonons arising from the minority compound with the density of states of the majority compound.