CURRENT TRANSPORT IN FREESTANDING POROUS SILICON

The electrical conduction of free-standing porous silicon layers, obta ined from n(+) silicon with various anodization currents and illuminat ion conditions, has been investigated in vacuum as a function of the t emperature in the interval 300-210 K. The two-contact I-V characterist ic is determined by the metal/porous silicon rectifying interface, whe reas, by using the four-contact technique, a linear dependence of the current vs voltage was found. The resistance of free-standing samples showed a thermally activated behavior, with activation energies rangin g from 0.1 to 0.44 eV. It was found that the activation energy decreas ed if the light intensity during the anodization was reduced. Variatio ns of activation energy were also observed if the anodization current was changed but, in this case, it was not possible to find any correla tion over the parameter range investigated. (C) 1996 American Institut e of Physics.