Absorption Spectrum of Germanium and Zinc-Blende-Type Materials at Energies Higher than the Fundamental Absorption Edge

Thin films of several III–V and II–VI zinc-blende-type semiconductors were prepared by vacuum evaporation. Germanium thin films were prepared by epitaxial vacuum evaporation onto CaF2 substrates. The absorption spectra of these films reveal, besides the fundamental absorption edge and its spin-orbit splitting, additional structure at higher energies. This structure has been interpreted along the lines followed in the interpretation of the reflection spectra of these materials. The agreement between the values for the various energy gaps derived from absorption and from reflection spectra is excellent.