Electrical characterization and fabrication of organic/inorganic semiconductor heterojunctions

Thin films of polyaniline (PANI) titanium dioxide (TiO₂) 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.