Abstract: The valence band offsets ΔE_v(x) as a function of the alloy compositon x of two typical lattice matched ternary alloy heterojunctions (AlP)_x(Si₂)_1-x/GaP and (GaP)_x(Si₂)_1-x/GaP are studied by using the average bond energy theory in conjunction with the cluster expansion method.It is shown that the variations of ΔE_v(x) at (AlP)_x(Si₂)_1-x/GaP and (GaP)_x(Si₂)_1-x/GaP are nonlinear and non monotonous.The calculated results of ΔE_v are in very good agreement with the data previously reported.

Key words: heterojunction, valence band offsets, average bond-energy