Implementation of Band-to-Band Tunneling Phenomena in a Multisubband Ensemble Monte Carlo Simulator: Application to Silicon TFETs

Abstract

TFETs are in the way to become an alternative to conventional MOSFETs due to the possibility of achieving low subthreshold swing (SS) combined with small OFF current levels which allows operation at low VDD. In this work, a non-local band-to-band tunneling (BTBT) model has been successfully implemented into a Multi-Subband Ensemble Monte Carlo (MS-EMC) simulator and applied to ultra-scaled silicon-based n-type TFETs. We have considered two different criteria for the choice of the tunneling path followed by the carriers when crossing the potential barrier, which leads to different distributions of the generated electron-hole pairs. Subband discretization due to field-induced quantum confinement has been taken into account. TCAD simulations accounting for quantization effects are considered for comparison purposes providing very accurate agreement with MS-EMC results.Index Terms-tunnel field-effect transistors, TFET, quantum confinement, band-to-band tunneling, BTBT, Multi-Subband Ensemble Monte Carlo, MS-EMC.

Impact of Strain on S/D tunneling in FinFETs: a MS-EMC study

“…On the other side, the additional modules needed for taking into account the quantum effects are included as separated transport mechanisms without increasing the computational time, which is a noteworthy advantage of our code in comparison to purely quantum transport simulations. In addition to the S/D tunneling [9], others tunneling mechanisms such as band-toband tunneling (BTBT) [10] and gate leakage mechanisms (GLM) [11] have been also incorporated in this MS-EMC tool. They can be activated or not depending on the simulation scenario, making possible their individual or simultaneous simulation [12].…”

Multisubband Ensemble Monte Carlo Analysis of Tunneling Leakage Mechanisms in Ultrascaled FDSOI, DGSOI, and FinFET Devices

“…Finally, the BTBT algorithm herein implemented calculates the nonlocal direct and phonon-assisted tunneling considering quantum confinement effects [18]. It is based on the Kane's model which translates the tunneling current into suitable generation rates [G BT BT (x,z)] for both electrons and holes.…”

“…Moreover, this tunneling path is dynamically modified in each simulation step according to the up-to-date electrostatic configuration given by our MS-EMC simulator. More details about the procedure followed to evaluate this F max trajectory can be found in [18] where it is also compared to another trajectory assumption in a silicon-based n-type tunnel FET. After the determination of the starting and ending points for the tunneling process, the electric field is computed by using those two points and the distance between them.…”

“…The BTBT model developed in this paper represents an improvement with respect to its previous version [18] as to the slice selection where the charge is injected. In the prior version, we only selected one slice and only its associated tunneling charge, resulting from integrating the generation rate across it, was injected in the selected slide.…”

NESS: new flexible Nano-Electronic Simulation Software

“…Quantum confinement and quantum transport phenomena dominate the transistor characteristics and have to be taken into account in simulations together with the charge and matter granularity and the complexity of the interface transitions. Simulation tools with different level of complexity including drift-diffusion (DD) with quantum corrections [1], 3D ensemble Monte Carlo (MC) [2], MultiSubband (MS) 2D [3] and 1D MC [4], direct Boltzmann Equation solvers [5], Non-Equilibrium Green's Function (NEGF) simulators in ballistic regime [6] and with scattering [7] have been developed by different software vendors and research groups. However, these simulators usually work in isolation and it is difficult to carry out consistent simulations for a particular transistor structure highlighting and understanding the areas of applicability and the additionality of simulation techniques with increasing complexity listed above.…”