Analysis of the thickness-dependent electrical characteristics in pentacene field-effect devices

Abstract

n this paper, we report on the important relationship among the capacitance-voltage (C — V ) characteristics of metal-insulator-semiconductor (MIS) capacitors, the output currents of pentacene-based organic field-effect transistors (OFETs), and the semiconductor layer’s thickness. The effect of the semiconductor layer’s thickness on the effective channel capacitance, when the MIS capacitors are fully accumulated with sufficient negative bias, was observed to be directly correlated with the magnitude of the saturated output current. The variation in accumulation capacitance of MIS capacitors due to changes in layer thickness is shown to indicate the existence of a channel capacitance. This determines the output currents in the saturation region. Furthermore, the accumulation capacitance appears to decrease notably when the thickness of the pentacene layer is reduced below 20 nm.