Low-field (third-derivative) electroreflectance spectra taken on fully depleted space-charge regions are shown to be linear in the modulation potential and free from experimentally induced line-shape distortions due to modulation wave-form, dc bias, or barrier-potential effects. Using a metal-semiconductor (Schottky diode) configuration, accurate threshold energies of the ${E_0}^{\prime }$ triplet of Ge are obtained. The observed spin-orbit-splitting energy of the valence band confirms that the highest transition also occurs at $\Gamma$.

• Received 21 January 1972

DOI:https://doi.org/10.1103/PhysRevLett.28.913