Theory of ballistic nanotransistors

Abstract

Numerical simulations are used to guide the development of a simple analytical theory for ballistic field-effect transistors. When two-dimensional (2-D) electrostatic effects are small (and when the insulator capacitance is much less than the semiconductor (quantum) capacitance), the model reduces to Natori's theory of the ballistic MOSFET. The model also treats 2-D electrostatics and the quantum capacitance limit where the semiconductor quantum capacitance is much less than the insulator capacitance. This new model provides insights into the performance of MOSFETs near the scaling limit and a unified framework for assessing and comparing a variety of novel transistors.

VHDL-AMS implementation of a numerical ballistic CNT model for logic circuit simulation

“…where E F is the Fermi level, q is the electronic charge and V SC represents the self-consistent voltage [1] whose presence in these equations illustrates that the CNT energy band is affected by external terminal voltages. The self-consistent voltage V SC is determined by the device terminal voltages and charges at terminal capacitances by the following non-linear algebraic equation [1], [6]:…”

“…The self-consistent voltage V SC is determined by the device terminal voltages and charges at terminal capacitances by the following non-linear algebraic equation [1], [6]:…”

“…According to the ballistic CNT transport theory [1], [10] the drain current caused by the transport of the non-equilibrium charge across the nanotube can be calculated using the FermiDirac statistics as follows:…”

“…Transistors using carbon nanotubes (CNTs) are expected to become the basis of next generation integrated circuits (ICs) [1], [2]. These expectations are motivated by the growing difficulties in overcoming physical limits of silicon-based transistors fabricated using current technologies.…”

“…A number of theoretical models have been created to describe the interplay between different physical effects within the nanotube channel and their effect on the performance of the device [3], [4], [5], [6], [7], [8]. The standard methodology of modelling CNTs is to derive the channel current from the non-equilibrium mobile charge injected in the channel when voltages are applied on the terminals of the transistor [1]. However, a common problem these models are facing is the complexity of calculating the Fermi-Dirac integral and non-linear algebraic equations which express the relationships between charge densities and the current.…”