Electronic structure of GaAs(001)

The bulk valence-band structure along the {Γ}X line of the GaAs(001)-c(4×{}4) surface prepared by molecular-beam epitaxy is investigated by angle-resolved photoemission using He i and synchrotron radiation with photon energies between 10 and 34 eV. In order to consider explicitly the final-state effects, the technique of structure plots is applied using free-electron-like final states as well as complete pseudopotential calculations for the unoccupied bands. In this way nearly all experimentally observed peaks can be consistently explained, except two peaks close to the valence-band maximum, which have to be attributed to surface states.