Regular Article

Static and dynamic modeling of organic thin film transistors: effect of channel length on the Mayer–Neldel rule energy and quasistatic capacitances

¹ Laboratoire de Physique des Matériaux, Structure et Propriétés, Groupe Physique des Composants et Dispositifs Nanométriques, Faculté des Sciences de Bizerte, Université de Carthage, 7021 Jarzouna-Bizerte, Tunisia
² Department d'Enginyeria Electronica, Universitat Politecnica de Catalunya, C/Jordi Girona, Modul C 4, 08034 Barcelona, Spain

^* e-mail: nawelarfaoui20@yahoo.fr

Received: 18 November 2017
Received in final form: 20 March 2018
Accepted: 3 April 2018
Published online: 8 June 2018

Abstract

In this work, pentacene based thin film transistors (TFTs) with different channel lengths (L = 2.5, 5, 10 and 20 μm) have been fabricated and characterized electrically. Exploiting the electrical characteristics, we have analyzed the channel length effect on the key parameters of fabricated TFTs. We found that the performance of pentacene-TFTs was enormously enhanced by the reduction of channel length .We have also examined the influence of contact and channel resistances (R_C and R_ch) on the electrical proprieties of fabricated TFTs, using the transmission line method (TLM). Then, we have modeled the dependence of the total resistance R_T on the gate voltage V_G using the grain boundary trapping Meyer–Neldel rule (GBT-MNR) model and we have successfully reproduced, the output characteristic of pentacene TFTs using the overall resistance extracted from the GBT-MNR model. Finally, in order to investigate the channel length effect on the dynamic behavior of fabricated devices, we have reported a dynamic model based on the quasistatic assumptions which were used for metal-oxide-semiconductor field-effect transistor (MOSFET). Accordingly, we have presented a simple small-signal equivalent circuit to calculate theoretically the capacitances of pentacene-TFTs for different channel lengths.