New transport phenomena probed by dielectric spectroscopy of oxidized and non-oxidized porous silicon

Dielectric spectroscopy accompanied by infrared (IR) and photoluminescence (PL) spectroscopy have been utilized to reveal the correlation between transport, optical and structural properties of oxidized porous silicon (PS). Three relaxation processes at low-, mid- and high-temperatures were observed, including dc-conductivity at high-temperatures. Both the low-T relaxation and the dc conductivity were found to be thermally activated processes that invlove tunneling and hopping in between the nanocrystals in oxidized PS. We have found that the dc-conductivity is limited by geometrical constrictions along the transport channels, which are not effected by the oxidation process and are characterized by activation energis of about ∼0.85 eV. The low-T relaxation process involves thermal activation followed by tunneling in between neighbor nanocrystals, with somewhat lower activation energies.