The Ga core exciton at unrelaxed GaAs (110)

Core excitonic effects at an unrelaxed GaAs (110) surface are studied using a localized orbital approach. A realistic Hamiltonian for the conduction bands is obtained with inclusion of 5s orbitals and third nearest neighbor interactions. The binding energies of core excitons both in the bulk and at the surface are calculated. The results are in good agreement with experimental measurements, with a contact potential of ∠l.0 eV. In addition it is shown that the binding energy has a maximum value and the limiting case can be thought of as an ideal vacancy.