T. K. Maiti

A Surface Potential Based Organic Thin-Film Transistor Model for Circuit Simulation Verified With DNTT High Performance Test Devices

A compact surface potential based model for organic thin-film transistors (OTFTs), including both tail and deep trap states across the band gap, is reported. The model has been developed on the basis of a complete surface potential approach for undoped-body OTFTs. Accurate surface potentials are calculated by explicitly including the floating backside potential that varies with applied biases. A pseudo-2D resistor model is developed to capture the structural features of the OTFT. The resistor model considers, in particular, the effects originating from a bias dependent 2D current flow in the channel region and results in accurate reproduction of the electrical characteristics. The fitting capability of the developed OTFT model is verified against measured high-performance dinaphtho thieno thiophene (DNTT) based field-effect transistor data. Accurate reproduction of the current characteristics of the OTFT test structures is verified from a week to a strong inversion regime.

Physically Based Compact Mobility Model for Organic Thin-Film Transistor

A physically based compact mobility model for organic thin-film transistors (OTFTs) with an analysis of bias-dependent Fermi-energy (EF) movement in the bandgap (Eg) is presented. Mobility in the localized and extended energy states predicts the drain-current behavior in the weak and strong accumulation operations of OTFTs, respectively. A hopping mobility model as a function of the surface potential is developed to describe the carrier transport through localized energy states located inside Eg. The Poole-Frenkel parallel-field-effect mobility and vertical-field-effect mobility are considered to interpret the bandlike carrier transport in the extended energy states. The parallel field effect on mobility is more pronounced for shorter channel length OTFTs and is considered by developing a channel-length-dependent mobility model. The vertical field effect on mobility is included to account for the effect of mobility on carrier transport at high gate-voltage-induced fields. We also compared the model results with 2-D device simulations and measurements to verify the developed mobility model.

Benchmarking of a surface potential based organic thin-film transistor model against C 10 -DNTT high performance test devices

In this paper, a surface potential based compact model for organic thin-film transistors (OTFTs) including both tail and deep trap states across the band gap is presented and benchmarked against measured data from high-performance dinaphtho thieno thiophene (C10-DNTT) based test devices. This model can accurately describe the OTFT test-structure current from week to strong inversion regime.

Modeling of electrostatically actuated fluid flow system for mixed-domain simulation

Modeling of an electrically driven fluid flow system for multi-domain simulation is reported. The electrically driven actuator force is considered by an actuator component model, based on a spring-mass-damper system with force balance formulation. The fluid flow model is developed on the basis of a Kirchhoffian network which is derived from the mass transport equation. The actuator and the fluid models are coupled through equivalent circuits, leading to a consistent approach of mixed-domain system simulation. This approach is applied to design a flexible blood pumping system where the blood flow is driven by electrical organic actuators. Modeled results are compared with 2D device simulation based on the finite element method.

Organic thin-film transistor compact model with accurate charge carrier mobility

A physical compact charge carrier mobility model for undoped-body organic thin-film transistors (OTFTs) based on an analysis of the bias-dependent Fermi-energy movement in the band gap is reported. Mobility in localized- and extended-energy states predicts the current transport in week- and strong-inversion regimes, respectively. A hopping mobility model as a function of surface potential is developed to describe the carrier transport through localized trap states located in the band gap. The Poole-Frenkel field effect mechanism is considered to interpret the band-like carrier transport mechanism in extended energy states. Modeled results are compared with the measured DNTT-based high-performance OTFTs data to verify the model.

Circuit-aging modeling based on dynamic MOSFET degradation and its verification

The reported investigation aims at developing a compact model for circuit-aging simulation. The model considers dynamic trap-density increase during circuit operation in a consistent way. The model has been applied to an SRAM cell, where it is believed that the NBTI effect dominates. Our simulation verifies that the hot-carrier effect has a compensating influence on the NBTI aging of SRAM cells.

Analysis of printed organic MOSFET characteristics with a focus on the temperature dependence

An experimental and theoretical investigation of the device characteristics of printed organic MOSFETs with a focus on the temperature dependence is reported. In particular, an anomalous behavior of the temperature dependence of the I ds–V gs characteristic is observed, which is found to be increased at higher temperature in MOSFETs fabricated with the printing technology. Our analysis suggests that the temperature dependence of the trap density and the carrier transport mechanism are the causes for this anomalous increase at higher temperature. The results obtained with the compact model HiSIM-Organic, developed based on the physics of carrier dynamics in organic materials, confirm these conclusions. Improving stable characteristics in circuit applications are demonstrated to be achievable at higher temperatures, due to these anomalous properties of organic MOSFETs fabricated by applying the printing technology.

Mixed-domain compact modeling framework for fluid flow driven by electrostatic organic actuators

A new modeling framework of an electrically driven fluid flow system for mixed-domain circuit simulation is reported. Coupling between electrical and fluidic domains is implemented by developing an organic actuator compact model. The actuator model is based on force balance spring-mass-damper system equation. Fluid compact model is derived from mass transport equation. The actuator and the fluid models are connected using circuit network. As an example, we applied the modeling framework for designing and optimizing an electrically driven blood flow system. We also compared the modeled results with finite element method (FEM) based numerical simulation.

Compact modeling of dynamic trap density evolution for predicting circuit-performance aging

Abstract It is shown that a compact MOSFET-aging model for circuit simulation is possible by considering the dynamic trap-density increase, which is induced during circuit operation. The dynamic trap/detrap phenomenon, which influences the switching performance, is also considered on the basis of well-known previous results. Stress-dependent hot-carrier effect and NBTI effect, origins of the device aging, are modeled during the circuit simulation for each device by integrating the substrate current as well as by determining the oxide-field change due to the trapped carriers over the individual stress-duration periods. A self-consistent solution can be obtained only by iteratively solving the Poisson equation including the dynamically changing trap density, which is achieved with negligible simulation time penalty. To enable accurate circuit-aging simulation, even for high-voltage MOSFETs, the carrier traps within the highly resistive drift region are additionally considered.

Physics based system simulation for robot electro-mechanical control design

The aim of our investigation is to develop complete electro-mechanical system simulation. The present developed prototype system includes pressure sensors, amplifiers, a controller, servo motors, and a robot-body. Sensor signals such as transduced voltage, servo motor actuation signals such as shaft angle, velocity, and acceleration are modeled in an analytical way. The entire system structure is formed based on the equivalent circuit concept. Mechanical dynamics of a two-leg robot-body is verified with the developed simulation system.