Effects of interband phototunneling and filling the bands in electroreflectance spectra of germanium

Abstract

Electroreflectance spectra of chemically etched (110) surface of intrinsic germanium are measured in the range of E₁, E₁ + Δ₁ transitions for ||[100] and ||[10] directions of the polarization vector. Separated are isotropic (surface) and anisotropic (bulk) electroreflectance components. The spectrum of the bulk electroreflectance component (the Keldysh-Franz effect), as it can be deduced from its phase, corresponds to the case when energy bands are bent up if going to the surface. This situation is possible in the conditions of filling the bands only at presence of an extremum in the semiconductor energy scheme. Appearance of this extremum can be related to the fact that the electron wave function at the surface is equal to zero or defermined by mirror image force action.