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 $s{p}^3$ and $\mathrm{Ga}-3\mathrm{}d$ valence bands and the conduction bands. The energy of $X_7^V$ is shown to lie at least 3 eV below ${\Gamma }_8^V$. 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 $\mathrm{Ga} 3d$-$X_6^C$ exciton binding energy is of the order of 100 meV.