Configuration entropy of ternary alloy superlattice

Difference in mixture-related entropy between superlattice and the corresponding homogeneous crystal in which all composition gradients have been annihilated by equilibrating processes (the configuration entropy of superlattice, ΔS_conf) is analytically formulated as a function of composition variables and geometry parameters. Numerical evaluations are performed for the important case of Al_xGa_1−xAs-based superlattice. Qualitative trends confirm in general the intuitive expectations (− ΔS_conf grows with increasing composition difference between the layers); the dependencies on geometry parameters exhibit a peculiar behaviour. The results are applicable to superlattices with periode lengths sufficiently in excess of the monoatomic layer thickness.