Electrical transport phenomena in nanostructured porous-silicon films

摘要

The charge transport mechanisms in nanostructured porous silicon (PS) films were studied through current-voltage (I-V) measurements ofplanar Au/PS/Au structures in dark conditions at 300 K. The films were formed by electrochemical etching of1?5 ?-cm p-type Si (100)wafers producing PS layers of4.48×109?-cm. The charge transport is limited both by the space charge limited currents (SCLC) andthe carrier trapping- detrapping kinetics in the inherent localized PS energy levels. I-V characteristics evolve according to the trapping-detrapping carrier kinetics in the films showing that applying external bias, the electrical current can be controlled. For the first time thetrap filling limiting voltage (VTFL) was identified in PS films that shift between 1 and 3 volts by the carrier trapping-detrapping kinetics fromthe PS intrinsic defect states. An energy band diagram for the films is schematically depicted including defect states. To give a reasonableexplanation of the found behavior the existence of a thin silicon oxide film covering the network-like-silicon-nanocrystallites is required, inagreement with the widely accepted PS film structural models.