Drift mobility of excess carriers in porous silicon

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Abstract
The time of flight technique is used to study experimentally the charge-carrier transport in porous silicon. The measured drift mobilities of electrons and holes show a decrease with the reduction of the typical size of structural elements of the porous material. The experimental transient characteristics reveal a strong spatial dispersion of the packet of drifting carriers. The parameters of the dispersion have been determined. The results are analyzed in terms of the dispersion model developed for structurally disordered semiconductors. The similarity and difference in the charge transport between porous silicon and disordered semiconductors are discussed. It is concluded that the dispersion results from the movement of carriers throughout a network of paths different in geometry and electrical properties.