Large drift-diffusion and Monte Carlo modeling of organic semiconductor devices

We have investigated electronic transport both in organic thin film transistors (TFTs) and in hybrid organic/inorganic Schottky diodes. In order to derive from basic principles the transport properties of the organic semiconductors we have developed a Monte Carlo-based transport simulator to calculate field and temperature dependent mobility. We have then modified a typical two-dimensional drift-diffusion simulator in order to account for organic transport effects. This simulator has been applied to study electron transport in Thiophene- and Pophyrin-based TFTs. The results, which are in good agreement with available experimental data, clarify the mechanism for field effect in these devices. In particular, we show how the transport occur in a very thin layer close to the SiO2 interface and that the channel conductance has a non-monotonic behavior has a function of drain voltage. We have also calculated the I-V characteristics of Ag/PTCDA/GaAs Schottky diode as a function of PTCDA thickness. The interplay between barrier height. PTCDA thickness and space charge limited current is outlined. (C) 2003 Elsevier Science B.V. All rights reserved.