Influence of carrier mobility and contact barrier height on the electrical characteristics of organic transistors

Abstract

We have investigated the electrical properties of organic thin-film transistors by way of two-dimensional drift-diffusion simulations. The dependence of the electrical characteristics on the mobility model and on the Schottky barrier height of the contacts is analyzed. We found that both the field dependence of the carrier mobility and the barrier height of the contacts are responsible for the nonlinearity of the output characteristics in the low bias region. We have then extracted the mobility from the simulated characteristics using standard metal–oxide–semiconductor analytic relations and compared to the mobility used in the simulation. The discrepancy found between the two mobilities is mainly induced by the presence of the contact barrier.

Ambipolar Field‐Effect Transistors Based on Solution‐Processable Blends of Thieno[2,3‐b]thiophene Terthiophene Polymer and Methanofullerenes

“…Such behavior is consistent with non-ohmic properties of metal-organic contacts when the injection barrier is higher than 0.3 eV, and is typically around 0.3-0.5 eV. [22][23][24] An injection barrier of ∼ 1 eV has been shown to cause severe contact resistance and to lead to very high nonlinearity in the FET output curves. [24] This observation leads us to conclude that fied gold surface work function can be estimated to be between 4.3 and 4.7 eV.…”

Gate-bias assisted charge injection in organic field-effect transistors

“…The origin is that for a given gate bias the barrier lowering increases with source-drain bias; since the total field at the source contact is enhanced. The S-shape has previously been attributed to an electric field dependent mobility [21,22]. Here we show that a large injection barrier described by thermionic emission and image-force lowering alone is sufficient.…”

“…In staggered transistors the contact resistance was attributed to the current-crowding effect and to a gate-dependent bulk resistance [18][19][20]. In a coplanar structure the contact resistance has been explained as the combined effect of a Schottky contact and a field-dependent mobility [21,22]. Although these physical effects enable a good modeling of the transistor characteristics;they are not able to explain why an OFET is more insensitive to the barrier height than an OLED [11][12][13].…”

Lithography‐Free Microfabrication of Electrode Arrays with 2 μm Electrode Gaps Using Topographic Templates

“…These features indicate a non-negligible contact resistance, which is prominent in bottom contact OTFT with short channel length on the order of several tens of microns. [ 20,[52][53][54] Representative transfer curves for TIPS-pentacene OTFTs with L = 2, 5, 7 and 11 µm are shown in Figure 3 ( Table 1 ). TIPS-pentacene OTFTs in this study exhibit large positive threshold voltages V T , which is common in other devices with similar confi gurations and surface treatments.…”