Recherche
Organic Field Effect Transistor Realization and Simulation
Organic electronics have been aggressively studied for applications in electronic displays, sensors, radio frequency identification tags, smart cards and organic solar cells. This large range of possible applications can be realized by understanding the basic science in involved in the operation of organic electronic devices and the physics of organic semiconductors.
The discovery of electrical conductivity in polymers enabled the production of organic electronic devices such as OFETs, OLEDs and OPVs. OFETs were first reported in 1986 and since then many advances in device performance have been made. The possibility of printing flexible electronic devices using OFETs has stimulated research devoted to discovering organic semiconductors with high conductivity and to optimizing device performance. This research section has been pioneering the R&D of organic electronics including organic field effect transistor OFETs based on N type polymeric semiconductor "ActiveInkTM N2200" (Figure II).
Figure II. Chimical Structure of ActiveInkTM N2200
We have fabricated N2200-based thin film transistors and analyzed their electrical properties with the help of two-dimensional drift-diffusion simulations which favorably compare with the experimental results. We have set up a model considering the intrinsic propreties of the polymer. We show how this model can be applied to different devices with different film thikness and we analyze the relationship between mobility and applied gate voltage. On the basis of the simulation results, we have introduced an effective carrier mobility, which accounts for hopping effect (Pool Frenkel). The comparison between experimental results and simulations allows us to clearly understand the differences in the mobility derived by the analysis of current–voltage curve (as done experimentally by using standard MOSFET theory) and the intrinsic mobility of the organic layer. The effect of the N2200/oxide interface traps and fixed surface charges has also been considered. The dependence of the threshold voltage on the density and energy level of the trap states has been outlined.
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Figure III. (a) TCAD simulation of BG/BC Organic Field Effect Transistor based PolyeraTM N2200 (b) transfer and output characteristics (experiments Vs simulations)
For more informations contact: bilel.hafsi@iemn.univ-lille1.fr
Single Electron Transistor "SET" Simulation
One of the most promising new devices based on new nanoscale physics is the single-electron transistor “SET”. A SET has an extremely small quantum dot in the channel. The number of electrons in the dot is precisely controlled by the Coulomb blockade, and a SET shows unique oscillatory I-V characteristics that are expected to have new functionalities. A great deal of research has been done on the realization of memory devices based on the single electron tunneling phenomena. A single electron memory “SEM” should work with a reasonable bit error rate, have low power, scalability to the sub-nanometer regime and extremely high charge sensitivity.
The functioning of the SET is based on the Coulomb blockade theory, which is a direct consequence of the discreteness of the electron charge. In order to develop the I-V characteristic, we start by analyzing the equivalent electrical model of SET using Kirchhoff voltage and current laws.
In MATLAB code, after we have taken some initialization, we have calculated the total energy variation and the rate for different configurations. In order to obtain Nopt there are many methods, we have chosen the Lientschnig method where:
Then we can calculate the different transition probabilities to finally get I-V characteristic. (for more informations link)
I-V Simulations: