Fundamental Reflectivity Spectrum of Semiconductors with Zinc-Blende Structure

The fundamental reflectivity spectrum of several III–V and II–VI semiconductors is discussed and compared with the reflectivity spectrum of the group IV semiconductors. A general feature of these spectra is the presence of two peaks within the fundamental absorption region. The lower energy peak, which corresponds to a maximum in the refractive index, can be split into a doublet. This peak is probably due to direct transitions between the valence band extrema in the 111 direction at the edge of the Brillouin zone (L point) and the corresponding conduction band minima. The splitting of this peak corresponds to the spin-orbit splitting of the valence band extrema (L3). The second peak corresponds to a maximum in the combined density of states for the transitions. The temperature dependence of these peaks is also discussed.