Electrical characterization of the polyaniline/p-silicon and polyaniline titanium dioxide tetradecyltrimethylammonium bromide /p-silicon heterojunctions

Au/PANI/p-Si/Al and Au/PANI TiO2 TTAB/p-Si/Al heterojunctions have been fabricated by spin coating of soluble polyaniline (PANI) and PANI titanium dioxide (TiO2) tetradecyltrimethylammonium bromide (TTAB) on the chemically cleaned p-Si substrates. The thicknesses of the polymeric films have been determined by a profilometer. The current–voltage (I–V) characteristics of the heterojunctions have been obtained in the temperature range of 98–258 K. These devices have showed the rectifying behavior such as diode. The I–V characteristics of the devices have been analyzed on the basis of the standard thermionic emission theory at low forward bias voltage regime. It has been shown that the values of ideality factor decrease while the values of barrier height increase with increasing temperature. This temperature dependence has been attributed to the presence of barrier inhomogeneities at the organic/inorganic semiconductor interface. Furthermore, analysis of the double logarithmic I–V plots at higher forward bias voltages at all temperatures indicates that transport through the organic thin film is explained by a space-charge-limited current process characterized by exponential distribution of traps within the band gap of the organic film. The total concentration of traps has been found to be 3.52 × 1014 cm− 3 and 3.14 × 1015 cm− 3 for PANI and PANI TiO2 TTAB layer, respectively.