Bonds in III-V quaternary alloy semiconductors of ${\mathit{A}}_{1\mathrm{-}\mathit{x}}^{\mathrm{III}}$${\mathit{B}}_{\mathit{x}}^{\mathrm{III}}$${\mathit{C}}_{1\mathrm{-}\mathit{y}}^{\mathrm{V}}$${\mathit{D}}_{\mathit{y}}^{\mathrm{V}}$ type

Relative numbers or statistics of bonds in III-V quaternary alloy semiconductors of ${\mathit{A}}_{1\mathrm{-}\mathit{x}}^{\mathrm{III}}$ ${\mathit{B}}_{\mathit{x}}^{\mathrm{III}}$ ${\mathit{C}}_{1\mathrm{-}\mathit{y}}^{\mathrm{V}}$ ${\mathit{D}}_{\mathit{y}}^{\mathrm{V}}$ type are uniquely determined through a thermodynamical approach in which the cohesive and the strain energies of bonds are taken as the enthalpy in the analysis. The valence-force-field model is used for calculating the strain energy, and the effect of local environment on the bond strain is considered. The analysis is applied to nine different quaternary alloy semiconductors composed of two elements of Al, Ga, or In as the group-III elements and two elements of P, As, or Sb as the group-V elements. The strain energy is a predominant factor in ${\mathrm{In}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Ga}}_{\mathit{x}}$ ${\mathrm{C}}_{1\mathrm{-}\mathit{y}}^{\mathrm{V}}$ ${\mathit{D}}_{\mathit{y}}^{\mathrm{V}}$ (${\mathit{C}}^{\mathrm{V}}$,${\mathit{D}}^{\mathrm{V}}$=P,As,Sb), the cohesive energy is a predominant factor in ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Al}}_{\mathit{x}}$ ${\mathit{C}}_{1\mathrm{-}\mathit{y}}^{\mathrm{V}}$ ${\mathit{D}}_{\mathit{y}}$, and both factors compensate each other almost completely in ${\mathrm{In}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Al}}_{\mathit{x}}$ ${\mathit{C}}_{1\mathrm{-}\mathit{y}}^{\mathrm{V}}$ ${\mathit{D}}_{\mathit{y}}^{\mathrm{V}}$. The results are interpreted on the basis of the bond-length dependence of each energy.