Schottky diodes based on electrospun polyaniline nanofibers: Effects of varying fiber diameter and doping level on device performance

Electrospinning is used to fabricate Schottky diodes using polyaniline nanofibers and n-doped Si. By varying the fiber diameter, and also by varying the fiber doping level at a fixed diameter, we compare the device performance and examine the role of surface states on barrier height and charge transport. The diode electrical characteristics were analyzed using the standard thermionic emission model of a Schottky junction. Clear rectification is observed for diodes fabricated from thick fibers with significantly reduced rectification ratios for diodes fabricated from thinner ones. The surface states on the semiconductor exert a weaker influence on diodes fabricated from thinner fibers due to the reduced junction area, and for the thinnest fiber where the depletion width is expected to be negligible, the analysis suggests an additional charge transport mechanism other than thermionic emission at the junction. On the other hand, varying the fiber doping level lowers the diode rectification ratio but other diode parameters are relatively unaffected.