Spectroscopic planar diffraction ellipsometry of Si‐based multilayer structure with subwavelength grating

Abstract

Spectroscopic ellipsometry has been applied at room temperature to a multilayer device structure with plain and nanograting‐embedded Si layer on the top. In both cases, the real and imaginary parts of the complex dielectric function of the top layer have been retrieved. In nanograting case, ellipsometric data were collected in planar diffraction geometry. A profound change in dielectric function in the photon energy region between 1.5 and 3.5 eV is established for nanograting‐embedded Si layer compared to plain Si layer. Both real and imaginary parts of the former are no longer Si‐like and resemble more those for metals. The maximum of interband density‐of‐states for optical transitions is positioned at 2.1 eV and coincides with the energy of optical transitions from the main irradiative eigenstate. The obtained results are discussed in terms of geometry‐induced doping changes in interband density of states.