Direct extraction of mobility in pentacene OFETs using C-V and I-V measurements

Mobility was extracted from top-contact pentacene organic field effect transistors with minimal assumptions. Low-frequency capacitance-voltage (C-V) measurements were used to calculate the sheet charge density of the channel, and current-voltage measurements with low drain-to-source voltage were used to extract mobility. The separation of charge and mobility with the use of C-V measurements illustrates that the mobility increases with gate voltage, differing significantly from mobility dependence on gate voltage in crystal silicon MOSFETs. The physical meaning of this mobility and the possible mechanism for the increase in mobility as a function of gate bias are discussed.

I. Introduction

Interest in pentacene organic field effect transistors (OFETs) has recently increased with the demonstration of functional logic circuitry and active-matrix liquid crystal display backplanes built with OFETs [1], [2]. OFETs may be fabricated at significantly lower temperatures than inorganic thin-film transistors (TFTs), which allows deposition of OFETs on a wide variety of large flexible substrates that might one day support large-area electronic devices such as electronic billboard displays.