Current Reduction Mechanism in Organic Thin Film Transistors

Hidden origin of current reduction mechanism in organic thin film transistor (OTFT) structure is investigated based on a device simulation, which makes it possible to derive current–voltage (I–V) characteristics, potential distribution and carrier concentration inside a device by solving Poisson's equation and continuity equation. It is made clear that the device performances improve more than twice to three hundred times only by inserting high impurity concentration layer under the source/drain contact region. The cause of the inferior characteristics of conventional OTFT devices is attributed to the deficiency of carriers in the channel region, resulting to a very high potential drop at the source–channel interface, thus leading to an apparent decrease of carrier mobility. These results clearly indicate the direction of OTFT technology development, i.e., development of high carrier concentration, or heavily doped organic semiconductor materials.