変位電流評価法で調べたペンタセン有機電界効果トランジスタ界面のキャリア挙動

抄録

We have carried out displacement current measurements to investigate the electrical properties of pentacene OFET (organic field-effect transistors) and their carrier injection behavior. We demonstrate that an analysis of displacement current provides us with information about (i) carrier injection from the metal electrodes to pentacene, (ii) the voltage at which carrier injection takes place, (iii) spatial distribution in the organic film of injected carriers, (iv) the amount of stored charge, and so on. We confirm that holes are injected from the Au electrode into the pentacene layer, which is consistent with the p-channel operation previously observed for pentacene OFET. We find that the gate voltage at which storage of injected charge at the gate oxide interface begins, is nearly equal to the onset voltage of the OFET, which suggests that carrier injection correlates with the operation of the FET. We also find that the electrical characteristics of pentacene FET greatly change due to exposure of the FET to oxygen. This change can be interpreted as being due to the carrier injection of the oxygen molecules adsorbed on the pentacene layer. We demonstrate that the drain current depends on the amount of injected carriers.