Electroreflectance of porous layers obtained by stain etching of laser modified silicon

Optical properties of an SiOx porous silicon (PS) interface, prepared by st ain etching of the laser modified p-Si surface, were investigated. The elec troreflectance spectra (ERS) were measured in the region of 3.0-3.8 eV. A c orrelation between the existence of photoluminescence (PL) and the polarity inversion of the ERS signal of PS, compared to the laser modified Si or PS samples without PL, is established. It is shown that PL appears due to the electron enrichment of the near interface region caused by the positive ch arge imbedded into the oxide layer. The transition energy experiences a red shift with the increasing thickness of the oxide film. The intrinsic field between the oxide layer and Si increased with the ageing of the PS samples displaying PL. The results obtained support the surface localization model of PS PL controlled by the tunnelling mechanism of photocarriers through t he Si/SiOx barrier.