Effects of cation order on the energy bands of GaAs-AlAs heterostructures

Pseudopotential band structure calculations of (GaAs)_n ? (A$\text{l}$As)_n with n = 1, 2, 3 and of Ga_0.5A$\text{l}$_0.5As show that the effects of cation order are small due to the weakness of the Ga-A$\text{l}$ potential difference. The energy bands of the n = 1 heterostructure can be obtained by folding those of the alloy except for small energy shifts and splittings which can be handled in perturbation theory. The superlattice energy gap decreases with increasing n, the shrinkage being 4 meV for n = 2 and 10 meV for n = 3.