Optical characterisation of porous silicon layers by spectrometric ellipsometry in the 1.5–5 eV range

Abstract

Spectroscopic ellipsometry study in the 1.5–5 eV range have been performed in 3 μm thick porous silicon layers, made on p and p + substrates and with porosities varying from 10% up to 86%. Above 2.5 eV, spectroscopic data are shown to depend on material morphology. Below 2.5 eV and for very high porosities, the PS films reveal an uniaxial optical anisotropy. A quantitative determination of this anisotropy, i.e., the bifregingence, in both p and p + porous films can be achieved.