Impact of source and drain contact thickness on the performance of organic thin film transistors

Abstract

This paper analyzes the impact of source (ts) and drain (td) contact thicknesses on top contact (TC) and bottom contact (BC) organic thin film transistors (OTFTs) with a gate in the bottom, using a benchmarked industry standard Atlas 2-D numerical device simulator. The parameters including drive current (Ids), mobility (μ), threshold voltage (Vt) and current on-off ratio (ION/IOFF) are analyzed from the device physics point of view on different electrode thicknesses, ranging from infinitesimal to 50 nm, for both top and bottom contact structures. Observations demonstrate that the performance of the BC structure is more affected by scaling of ts/d in comparison to its counterpart. In the linear region, the mobility is almost constant at all the values of ts/d for both structures. However, an increment of 18% and 83% in saturation region mobility is found for TC and BC structures, respectively with scaling down ts/d from 50–0 nm. Besides this, the current on-off ratio increases more sharply in the BC structure. This analysis simplifies a number of issues related to the design and fabrication of organic material based devices and circuits.