The alignment of the electronic band structures at contacts between solids is defined by the continuum of interface-induced gap states and the charge transfer across the interface. The barrier heights of metal–semiconductor contacts as well as the band edge discontinuities of semiconductor heterostructures are primarily described by the zero-charge-transfer barrier heights. This characteristic semiconductor property equals the energy distance between the majority-carrier band edge and the charge-neutrality level of the interface-induced gap states. The compositional trends of barrier heights of Al1−xInxAs, In1−xGaxAs, and Al1−xGaxAs Schottky contacts and of valence-band offsets of Al1−xGaxAs/GaAs heterostructures are analyzed. The zero-charge-transfer barrier heights of ternary compounds are found to vary linearly as a function of the compositional parameter x.