Current–voltage characteristics and inhomogeneous barrier height analysis of Au/poly(o-toluidine)/p-Si/Al heterojunction diode

Abstract

Thin films of poly(o-toluidine) (POT) with amorphous structure were prepared onto the surface of p-Si single crystal by spin coating technique. The electrical conduction mechanisms and related parameters of the Au/POT/p-Si/Al heterojunction diode were investigated using current–voltage (I–V) characteristics in temperature range 298–378 K. The device showed rectifying behavior. At relatively low forward applied voltages; the current through the junction has been analyzed on the bases of the standard thermionic emission theory. The ideality factor decreases with increasing temperature, whereas the barrier height increases. This behavior could be elucidated in terms of inhomogeneity model of barrier heights. In addition, the values of series resistance, ideality factor and effective barrier height at zero-bias are determined at different temperatures by using Cheung’s functions. At relatively high forward bias voltages, analysis of the double logarithmic I–V characteristics indicates that transport through the device is controlled by a space-charge-limited current process characterized by single trap of distribution in which the related parameters are estimated. Data analysis in reverse direction showed that the current can be described in terms of Poole–Frenkel mechanism at low applied voltage and in terms of Schottky mechanism at higher applied voltage.