Evaluation of organic metal-oxide-semiconductor capacitors based on a distributed constant circuit

The capacitance characteristics of pentacene metal-oxide-semiconductor (MOS) capacitors with a large uncovered pentacene area have been investigated. The capacitance measured was examined by assuming that the uncovered area is represented by a distributed constant circuit. The frequency dependence of the capacitance was reproduced by an equation derived based on the assumption. The sheet resistance for the uncovered area of a MOS capacitor was calculated as a function of the gate voltage from the capacitance measured. The mobility of a MOS capacitor with an uncovered area was estimated by fitting a curve to the gate voltage dependence of the sheet resistance, and was in the range of 0.48-0.64 cm2 V−1 s−1. In addition, the mobilities were compared with those calculated from the current-voltage characteristics of pentacene transistors fabricated on the same substrate.