Conductivity and distribution of charge on electroluminescent Si/SiO2 structures investigated by electrostatic force microscopy

Electroluminescent Si/SiO2/Au layer structures on a p-Si wafer are investigated with electrostatic force microscopy and atomic force microscopy. The samples comprise either four Si/SiO2 layer pairs prepared by chemical vapor deposition or a SiO2 thermal oxide layer grown at 950 degreesC on the wafer. A 9-13 nm thick Au-film electrode is sputtered on top of the samples. A correlation between the density of electroluminescent dots and distribution of charge on the surface of these structures is found. Measurements of the excitation current through the samples show that the four-layer Si/SiO2/Au structure has Poole-Frenkel type conductivity and the thermal oxide sample is excited through Fowler-Nordheim tunneling. (C) 2003 Elsevier B.V. All rights reserved.