Spectroscopic ellipsometry characterisation of light-emitting porous silicon structures

Abstract Large differences are observed in the 〈 n 〉 spectra of porous Si produced in n + , p + , p - substrates. Loss of c-Si structure is explained by a reduction in effective crystallite size due to quantum wire formation and does not require inclusion of an amorphous phase. Critical point energy shifts are attributed to confinement and stress effects. Spectroscopic ellipsometry is used to obtain porosity and detect porosity gradients.