Displacement Current Measurement as a Tool to Characterize Organic Field Effect Transistors

In spite of recent extensive studies of organic field effect transistors (OFETs), the operation mechanism is not yet clear. Especially the origin of the carriers accumulated in channel of OFET should be clarified to discuss the performance of OFETs. We have to take care of impurity-induced-carriers as well as carriers injected from source and drain electrodes. The spread of the charge sheet at organic/dielectric interface is also critical to the PET performance. Thus an experimental technique to probe such behavior of carriers is highly required. In this study, we have proposed displacement current measurement (DCM) method as a tool to characterize OFETs. We found that this technique enables us to probe various properties in OFETs; the carrier injection from metal electrodes to organic materials, the effective area of charge sheet in the channel, and the amounts of carriers accumulated in the device. The results for pentacene and poly-3- hexylthiophene FETs are reported to discuss the relation between the carrier generation and FET performance.