We report an analytical model for organic thin-film transistors that accounts for the influence of trap states on the current voltage characteristics. As the subthreshold regime sensitively reacts to the presence of traps, it is used to extract approximate trap parameters from experimental transistor data. To demonstrate the capability of our method, a comparison with the results of 2-D drift-diffusion simulations is provided.

Analytical Model of Trapping Effects in Organic Thin-Film Transistors

A PSPICE model for organic thin-film transistors (OFETs) employing poly(3-hexylthiophene-2,5-diyl) (P3HT) is derived. This model is based on the standard MOSFET Berkeley Short-channel IGFET Model equations, where the voltage dependences of the charge carrier mobility and the bulk conductivity are modeled by additional voltage-controlled current sources. The model requires only five additional parameters, which can be extracted from the output characteristics of the device. The model equations have been verified by device simulations, and the simulation results have been compared with measurements of P3HT OFETs.

A Physical-Based PSPICE Compact Model for Poly(3-hexylthiophene) Organic Field-Effect Transistors

We employ a physics-based model for hot-carrier degradation (HCD), which includes three main sub-tasks: the carrier transport module, a module describing interface state generation and a module for the simulation of the degraded devices. We examine different realizations of the model: with the transport module represented by Monte-Carlo, energy transport and drift-diffusion schemes. The main version, based on the Monte-Carlo approach, is able to represent HCD observed in different MOSFETs using the same set of the model parameters. These parameters have reliable and physically reasonable values. Therefore, we check whether two other versions are capable of the same representation (with the same parameters) or not. It appears that the simplified treatments fail to describe the degradation in devices of the same architecture but with different channel lengths employing a unique set of parameters. This circumstance suggests that a comprehensive HCD model has to be based on a rigorous solution of the Boltzmann transport equation (e.g. by means of a Monte-Carlo method).

/pdf/impact-of-the-carrier-distribution-function-on-hot-carrier-4eb059vwvu.pdf

Impact of the carrier distribution function on hot-carrier degradation modeling

Electrolyte-Gated Organic Field-Effect Transistors (EGOFETs) represent a class of organic thin-film transistors suited for sensing and biosensing in aqueous media, often at physiological conditions. The EGOFET device includes electrodes and an organic semiconductor channel in direct contact with an electrolyte. Upon operation, electric double layers are formed along the gate-electrolyte and the channel-electrolyte interfaces, but ions do not penetrate the channel. This mode of operation allows the EGOFET devices to run at low voltages and at a speed corresponding to the rate of forming electric double layers. Currently, there is a lack of a detailed quantitative model of the EGOFETs that can predict device performance based on geometry and material parameters. In the present paper, for the first time, an EGOFET model is proposed utilizing the Nernst-Planck-Poisson equations to describe, on equal footing, both the polymer and the electrolyte regions of the device configuration. The generated calculations exhibit semi-qualitative agreement with experimentally measured output and transfer curves.

/pdf/nernst-planck-poisson-analysis-of-electrolyte-gated-organic-37644uqxry.pdf

Nernst-Planck-Poisson analysis of Electrolyte-Gated Organic Field-Effect Transistors

Herstellung und Charakterisierung

Physics-based models of organic field-effect transistors (OFETs) which can be used for computer-aided simulation of organic integrated circuits were investigated. For this purpose hybrid OFETs with poly(3-hexylthiophene-2,5-diyl) as the semiconductor were fabricated and characterized. The differential drain-source resistance reveals the need for a unified consideration of a gate-voltage-dependent mobility and of the depletion effect. We avoid neglecting the capacitance of the insulator and the semiconductor which would have otherwise introduced restrictions. The analytic modeling yields a compact static equivalent circuit diagram.

Static model for organic field-effect transistors including both gate-voltage-dependent mobility and depletion effect

The functionality of nonvolatile memories with lateral multi-bit charge storage capabilities like NROM/TwinFlash is critically related to spatial separation of the injected charge quantities to discriminate different logical states. In this paper we develop an adapted methodology to extract local charge densities based on the constant field charge pumping method. Our method overcomes the problem of non self-consistency of conventional constant field charge pumping by determination of the spatial coordinate after every injection step. The method is demonstrated to directly extract the electron/hole mismatch after program and erase injection.

W. von Emden

Papers

Static model for organic field-effect transistors including both gate-voltage-dependent mobility and depletion effect

A modified constant field charge pumping method for sensitive profiling of near-junction charges