Effect of Trap Density on Carrier Propagation in Organic Field-Effect Transistors Investigated by Impedance Spectroscopy

Abstract

The effect of interfacial traps at the organic semiconductor and insulating oxide interface in a pentacene organic field-effect transistor was examined by both DC and AC methods, represented by the steady-state current-voltage condition and impedance spectroscopy, respectively. A comparative technique for the observation of the effects of low and high trap densities on carrier injection and transport was proposed. An equivalent circuit based on the transmission line model was used to model the system, and the measured results across various biases showed very good fit to this model. We found that for high trap densities, the contact resistance increased markedly, and consequently affected the transport properties, which led to the disappearance of the typical space-charge-limited condition. The mobility under AC bias was also much lower than that under DC bias, which was likely due to the trapping-and-release process involved in the AC bias but not in the DC bias. #

Conservation of the injection and transit time ratio in organic field-effect transistors: A thermally accelerated aging study

“…The deep trap device has a contact resistance with an order of magnitude more than the shallow trap device, which is in agreement with the previous reports. 21,25 Although further accelerated aging does not strongly influence the R c value, the change due to aging is comparable with the decrease in the effective mobility as depicted in Fig. 3(b).…”