Investigation of the Unoccupied Density of States in III-V Semiconductors by Optical Spectroscopy

A modified many angle reflection method based on the use of synchrotron radiation has been applied to study the optical constants of GaAs and GaP in the spectral range from 14 to 26eV. Experimental data on the energy dependence of the density of unoccupied band states have been obtained from the imaginary part of permittivity, where transitions from the 3d-core levels of Ga atoms can be observed. The experiment has been found in a good agreement with theoretical ab initio calculations of the density of p-states in both investigated materials.