VISIBLE CHEMILUMINESCENCE AND ELECTROLUMINESCENCE OF POROUS SILICON

The visible luminescence of porous silicon electrodes is reported. Both n-type and p-type material show similar characteristics. Three potential ranges can be distinguished. At open-circuit potential in the presence of certain strong oxidizing agents, e.g. Ce4+ and MnO4-, emission due to chemiluminescence (CL) occurs. At negative potential in the range of H-2 evolution, hole injection by a strong oxidizing agent. e.g. H2O2 and S2O82-, results in electroluminescence (EL). The intensities of CL and EL depend on the applied potential. When porous silicon is anodically oxidized, emission also occurs; this is probably due to CL. Because of the close resemblance of the luminescence of porous silicon to the photo- and chemiluminescence of siloxene, the emission from porous silicon is ascribed to the presence of siloxene or siloxene-like groups. The porous layer can be described as a discrete semiconductor with a large band-gap.