Current transport at the p-InP|poly(pyrrole) interface

The interface between the inorganic semiconductor p-type InP and the conjugated polymer poly(pyrrole) exhibits the electrical characteristics of a Schottky diode. Capacitance-voltage measurements yield an average barrier height of 0.62 +/- 0.01 eV at temperature T =298 K. At the same temperature, the empirical quality factor, extracted from current-voltage measurements, is near unity. However, the current-voltage measurements show a deviation from thermionic emission theory as the temperature is reduced, as witnessed by the increase of the quality factor and the curvature in the Richardson plot. Such deviation is best explained by the barrier inhomogeneity model, in which the barrier becomes voltage dependent due to the interaction of a small low-barrier region with a higher surrounding potential, termed the "pinch-off" effect. Traditional current-voltage models, including image force lowering or an interfacial layer, cannot predict the temperature dependence of the current-voltage data, although thermionic field emission may facilitate current transport in the interfaces with a higher doped InP substrate. Furthermore, the probability of sufficiently energetic incident charge carriers crossing the interface, termed the transmission coefficient, is smaller than that observed in metal Schottky diodes. (C) 2001 American Institute of Physics.