Determination of Optical Constants: Interband Transitions in Amorphous Ge, Si, and Se

Ellipsometric measurements are made of the optical constants of amorphous Ge, Si, and Se in the range of interband transitions between 2.0 and 4.0 eV. The results are discussed within the non‐direct transition model. For Ge and Se the discussion indicates transition between flat regions of the initial and final states with energy gaps of ≈ 1.35 and ≈ 2.0 eV, respectively. For Si the density of states behaves like some power of energy with a gap ≈ 1.45 eV. To explain the optical constants at photon energies > 3.0 eV energy dependent densities of states and/or matrix elements must be taken into account for all the three amorphous materials.