We present experimental valence-band optical densities of states for Si, Ge, and GaAs obtained from ultraviolet photoemission energy distribution curves obtained at about 25 eV of photon energy. The width of the upper two valence bands of Si and the positions of several energy-band minima for the second and third valence bands of Ge and GaAs have been accurately determined. Comparing the above-mentioned band edges with theoretical calculations based on optical data, we find good agreement for Si and observe significant differences for Ge and GaAs.
Grobman et al. (1972) studied this question.