Electrical characterization and fabrication of organic/inorganic semiconductor heterojunctions

Thin films of polyaniline (PANI) titanium dioxide (TiO 2 ) nanocomposites prepared with and without surfactant (tetradecyltrimethylammonium bromide, TTAB) were formed by spin coating onto chemically cleaned p-type silicon substrates. The current–voltage characteristics of the Au/PANI TiO 2 / p - Si/Al and Au/PANI TiO 2 TTAB / p - Si/Al heterojunctions had rectifying behavior with the potential barrier formed between the polymeric thin films and p - Si semiconductor, and they were analyzed on the basis of the standard thermionic emission (TE) theory. Cheung functions combined with conventional forward I – V characteristics were used to obtain diode parameters such as barrier height, ideality factor and series resistance ( R s ). The values of barrier height, ideality factor and R s were found as 0.496±0.003 eV, 2.313±0.067 and 23.633±7.554 Ω for the Au/PANI TiO 2 / p - Si/Al device; 0.494±0.003 eV, 2.167±0.018 and 12.929±2.217 Ω for the Au/PANI TiO 2 TTAB / p - Si/Al device. In addition, the energy distributions of the interface state density of the devices were determined from the forward I – V characteristics by taking into account the bias dependence of the ideality factor and barrier height. It was seen that the PANI TiO 2 TTAB / p - Si device had slightly higher interface state density values than those of the PANI TiO 2 / p - Si device.