Angle-resolved constant-initial-state spectroscopy (ARCIS) from the valence-band maximum (VBM) as initial state was used to determine conduction-band energies at the Γ point up to 66 eV above the VBM for GaSb and GaP. With the help of nonlocal-empirical-pseudopotential (EPM) calculations, structure in the ARCIS spectra up to 17 eV can be assigned to particular interband transitions. The experimental results are discussed in light of our previous work on the conduction-band states of GaAs, InP, and InAs. Above 40 eV there appears to be no correspondence between conduction-band states as calculated in the EPM framework and structure in the spectra. Autoionizing resonances due to surface core excitons have been observed in both materials. From their energies a surface core-exciton binding energy of 0.6 eV for GaSb and 1.4 eV for GaP has been determined.

• Received 4 August 1993

DOI:https://doi.org/10.1103/PhysRevB.48.14301