Measurements and modelling of the barrier heights and ideality factors in the metal/conducting polymer composite Schottky device

Metal/polymer Schottky contacts have been fabricated using electrochemicall y prepared free standing thin films of conducting polyaniline/polycarbonate composite as well as conducting polyaniline pellets with various metals su ch as Al, In, Pb and Sn. The current-voltage characteristics have been stud ied from room temperature down to 100 K. The data have been analyzed and in terpreted on the basis of the thermionic emission mechanism. The barrier he ight varies from 0.6 to 0.7 V for pellet and from 0.7 to 0.8 V for composit e films. There is little dependence of metal on the work function. The idea lity factor is dependent on the amount of polyaniline incorporation in poly carbonate, as indicated by the shift in the carbonyl peak in the Fourier tr ansform infrared spectrum. The abnormal decrease in barrier height and incr ease of ideality factor with decrease in temperature have been interpreted assuming a Gaussian distribution of barrier heights at the interface. This takes account of the nonuniformity and inhomogeneities at the interface. As in the case of inorganic semiconductor diodes, the analysis indicates an a pparent decrease in zero bias height and nonlinearity in activation plots. The bias dependence of barrier height and standard deviation causing an inc rease in ideality factor at low temperature has also been explored. (C) 199 9 American Institute of Physics. [S0021-8979(99)01406-1].