Key factors affecting contact resistance in coplanar organic thin-film transistors

Abstract

We present a comprehensive numerical analysis of contact resistance in coplanar organic thin-film transistors. A large number of hole-transporting organic transistors are investigated through two-dimensional finite-element simulation, by deliberately changing the channel length, source/drain electrode thickness, and hole-injection energy barrier heights. Gate-field-dependent terminal contact resistances of these devices are fully estimated and electrostatic distributions inside the organic semiconductor film are visualized for the understanding of physical mechanisms. It is found that the relationship between source/drain electrode thickness and contact resistance does not follow any simple trend and is also strongly associated with the injection energy barrier. Moreover, the origin of negative contact resistance in organic transistors featuring a minimal charge-injection barrier is elaborated. Finally, a direct impact of the semiconductor charge-carrier mobility on contact resistance is addressed, revealing a linear dependence of contact resistance on inverse mobility over a broad parameter range.

High-Performance Organic Source-Gated Transistors Enabled by the Indium-Tin Oxide–Diketopyrrolopyrrole Polymer Interface

“…For a theoretical investigation and parametrization of our organic SGTs, numerical modeling was carried out using a two-dimensional (2D) finite-element solver (ATLAS, Silvaco). This tool or equivalent tools have been widely used in device research. ,,,,, Its key principles are briefly introduced. Poisson’s equation links the spatial potential variation to the local space charge by div ( ε ∇ ψ ) = prefix− ρ where ψ is the electrostatic potential, ε is the material permittivity (which is the material dielectric constant k multiplied by the vacuum permittivity ε 0 ), and ρ is the space charge density.…”

“…This tool or equivalent tools have been widely used in device research. 8,9,28,30,37,38 Its key principles are briefly introduced. Poisson's equation links the spatial potential variation to the local space charge by…”

“…This tool or equivalent tools have been widely used in device research. 8,9,28,30,37,38 Its key principles are briefly introduced. Poisson's equation links the spatial potential variation to the local space charge by (1) where ψ is the electrostatic potential, ε is the material permittivity (which is the material dielectric constant k multiplied by the vacuum permittivity ε 0 ), and ρ is the space charge density.…”

“…Organic transistors are considered as a key element of future flexible and printed electronics technologies. − Contact effects are generally quite significant in organic transistors due to the disordered nature of metal/semiconductor interfaces and the low electrical conductivity of organic materials. − Therefore, reducing contact resistance has been an important motivation for organic transistor research. , However, the fact that a considerable equilibrium E b and an efficient gate modulation of contact resistance are easily observed in organic transistors can actually be a useful element to build extensively contact-limited systems such as SGTs or Schottky-barrier TFTs. , This may also imply a competitive edge for the simple structure and facile fabrication of organic-based SGTs as compared to inorganic SGTs that typically require sophisticated contact doping and/or a tunneling layer deposition to maintain a sufficient amount of E b . Despite these potential advantages of organic semiconductors, the research into organic SGTs has not been a mainstream topic in the broad organic transistor community so far.…”

Vertical organic transistors with a permeable base: from fundamentals to performance prediction

“…A finite-element two-dimensional (2D) device simulator (ATLAS, Silvaco) was used for the numerical modeling and simulation of OPBTs. [22][23][24] The Poisson equation connects the variation of local electrostatic potential (c) to the space-charge density (r) through div(erc) = Àr,…”