Temperature dependence of the current–voltage characteristics of Sn/PANI/p-Si/Al heterojunctions

Sn/PANI/p-Si/Al heterojunctions were fabricated by electropolymerization of aniline on chemically cleaned p-Si substrates. Current-voltage characteristics of Sn/PANI/p-Si/Al heterojunctions measured in the temperature range 140-280 K are presented and analyzed. Although these devices were clearly rectifying, their I-V characteristics were non-ideal, which can be judged from the nonlinearity in the semi-logarithmic plots. The high values of the ideality factor n depending on the sample temperature may be ascribed to a decrease of the exponentially increasing rate in current due to space-charge injection into the PANI thin film at higher forward bias voltages. Careful analysis of the forward bias I-V characteristics on a log-log scale indicates that the space-charge-limited current (SCLC) conduction controlled by an exponential trap distribution above the valence band edge dominates the current transport in the PANI/p-Si diodes at high voltages. Furthermore, the PANI was characterized by using Fourier transform infrared (FTIR) and ultraviolet-visible (UV-vis) spectra.