Electroreflectance of GaSb from 0.6 to 26 eV

Schottky barrier electroreflectance spectra are reported for GaSb from 0.6 to 26 eV. Accurate energies are determined for a number of critical points between the sp³ and Ga-3d valence bands and the conduction bands. The energy of X₇V is shown to lie at least 3 eV below Γ₈V. This is below the value obtained from local pseudopotential calculations and the x-ray photoemission assignments, but follows a trend previously established by nonlocal pseudopotential calculations for Ge and GaAs. The Ga 3d-X₆C exciton binding energy is of the order of 100 meV.