Understanding the effect of semiconductor thickness on device characteristics in organic thin film transistors by way of two-dimensional simulations

This paper investigates the dependence of organic thin film transistor (OTFT) characteristics with semiconductor (pentacene) thickness by way of two-dimensional drift–diffusion simulations. The extracted field-effect mobility of the as-measured top contact devices exhibits a variation as the pentacene thickness changes from 10 to 100 nm. Device simulation of an ideal OTFT does not exhibit any dependence on semiconductor thickness, as expected. Therefore, in simulations, the physical behavior related to charge transport at the pentacene–insulator interface and in the bulk is systematically introduced in order to model the experimentally observed device characteristics. These effects are simulated by incorporating a low-mobility-layer adjacent to the dielectric, and energy level shift in the same layer as compared to the bulk pentacene to induce confinement towards the insulator, and bulk donor traps in the pentacene film above a certain thickness (∼35 nm). Finally, verification between the simulated and experimental device characteristics is obtained as a function of pentacene thickness.