Investigation of the Transport Properties of Silicon Nanowires Using Deterministic and Monte Carlo Approaches to the Solution of the Boltzmann Transport Equation (original) (raw)
Related papers
IEEE Transactions on Electron Devices, 2000
We study electronic transport in silicon nanowire transistors at room temperature based on the self-consistent numerical solution of the multisubband Boltzmann transport equation and Poisson equation. The Schrödinger equation with nonparabolic corrections is solved in order to obtain the multisubband structure. Relevant microscopic scattering mechanisms due to acoustic and intervalley phonons, surface roughness, and ionized impurities are included in the simulation. A fluxconserving discretization scheme based on the uniform total energy grid is employed to avoid excessive numerical diffusion originating from the conventional kinetic-energy-based upwind scheme. We report an interesting kink behavior in the output characteristics and study the electron energy distribution inside the transistor as a function of bias conditions and scattering mechanisms.
Electron Mobility in Silicon Nanowires
IEEE Transactions On Nanotechnology, 2000
The low-field electron mobility in rectangular silicon nanowire (SiNW) transistors was computed using a self-consistent Poisson-Schrödinger-Monte Carlo solver. The behavior of the phonon-limited and surface-roughness-limited components of the mobility was investigated by decreasing the wire width from 30 nm to 8 nm, the width range capturing a crossover between twodimensional (2D) and one-dimensional (1D) electron transport. The phonon-limited mobility, which characterizes transport at low and moderate transverse fields, is found to decrease with decreasing wire width due to an increase in the electron-phonon wavefunction overlap. In contrast, the mobility at very high transverse fields, which is limited by surface roughness scattering, increases with decreasing wire width due to volume inversion. The importance of acoustic phonon confinement is also discussed briefly.
Electron dynamics in silicon nanowire using a Monte-Carlo method
Journal of Physics: Conference Series, 2009
We present a theoretical study of electron transport in silicon nanowire (SNW). A self-consistent 2D-Poisson-Schrödinger solver provides the band structure. Then, both electron velocity and low-field electron mobility along the SNW axis are computed with an ensemble Monte-Carlo method. Scattering mechanisms due to phonons (acoustic phonons, zero-order and first-order intervalley phonons) and surface roughness are taken into account. We investigate the effect of cross section size and transverse electric field on electron mobility in SNW.
Electron mobility in gate all around cylindrical silicon nanowires: A Monte Carlo study
International Conference on Microelectronics, 2010
Electron mobility in gated silicon nanowires is calculated using a Monte Carlo simulation that considers phonon and surface roughness scattering. Surface roughness scattering rates are calculated using Ando's model. The eigenenergies and eigenfunctions required for scattering rate calculation are determined by self-consistent solution of the Schrödinger and Poisson equations. The effects of size quantization and transverse electric field on electron
Hierarchical simulation of transport in silicon nanowire transistors
Journal of Computational Electronics, 2008
We propose a very fast hierarchical simulator to study the transport properties of silicon nanowire FETs. We obtain the transverse wave functions and the longitudinal effective masses and band-edges of the lowest conduction bands from a nearest-neighbor sp 3 d 5 s * tight-binding study of an infinite nanowire with null external potential. Then we plug these parameters into a self-consistent Poisson-Schrödinger solver, using an effective mass approach and considering the bands decoupled. We apply this method, which gives quantitatively correct results with notable time savings, for the simulation of transport in two different silicon nanowire FETs.
Microelectronics Journal, 2013
In this work we investigate the ballistic ratio and the backscattering coefficient in nanowire FETs operating under quasi-ballistic conditions. Starting from general expressions of the current-voltage characteristics worked out in a previous paper, we extract the above parameters and their functional dependence on inversion-layer charge and device length. The computation is based on a rigorous analytic solution of the BTE and on a numerical solution of the coupled Schrödinger-Poisson equations, by which multiple subbands are taken into account. We propose three different definitions of the ballistic ratio, clarify their meaning and compute their values against the gate voltage and the device length. As opposed to most phenomenological treatments addressing this subject for 2D nanoscale MOSFETs, the strength of our approach is that the aforementioned parameters can be computed from the knowledge of the scattering probabilities, without introducing any major simplifying assumptions.
Analytical Study of Carriers in Silicon NanoWires
MASAUM Journal of Basic and Applied Sciences , 2009
The limitations on carrier (holes and electrons) drift due to high-field streamlining also randomly velocity vector in equilibrium is reported. Asymmetrical distribution function that converts randomness in zero-field to streamlined one in a very high electric field is employed. The ultimate drift velocity is found to be appropriate thermal velocity for a given dimensionality for non-degenerately doped nanostructure. However, the ultimate drift velocity is the Fermi velocity for degenerately doped nanostructures. Quantum and high-field effects controlling the transport of carrier in nanostructures are described. The results obtained are applied to the modeling of a nanowire transistor.
Semiclassical transport in silicon nanowire FETs including surface roughness
Journal of Computational Electronics, 2008
In this paper we investigate the effect of surface roughness scattering on transport in silicon nanowire FETs using a deterministic Boltzmann equation solver previously developed by the authors. We first solve the coupled Schrödinger-Poisson equations to extract the subband profiles along the channel, and then address the transport problem. Some features of the low-field mobility as a function of the wire diameter and gate bias are discussed and the effect of surface roughness on the I–V characteristics is presented.
IEEE Transactions on Electron Devices, 2000
An efficient approach for the simulation of electronic transport in nanoscale transistors is presented based on the multisubband Boltzmann transport equation under the relaxation time approximation, which takes into account the effects of quantum confinement and quasi-ballistic transport. This approach is applied to the study of electronic transport in circular gate-all-around silicon nanowire transistors. Comparison with the nonequilibrium Green's function method shows that the new method gives reasonably accurate terminal characteristics. We study the influence of silicon body diameter and gate length on the terminal current and subthreshold slope (SS). We have found that the calculated ON current is inversely proportional to the gate length to the power 1/2, and that the silicon body diameter should be smaller than roughly 2/3 of the channel length in order to maintain the SS within 80 mV/dec.
One-dimensional multi-subband Monte Carlo simulation of charge transport in Si nanowire transistors
2016 International Conference on Simulation of Semiconductor Processes and Devices (SISPAD), 2016
In this paper, we employ a newly-developed one-dimensional multi-subband Monte Carlo (1DMSMC) simulation module to study electron transport in nanowire structures. The 1DMSMC simulation module is integrated into the GSS TCAD simulator GARAND coupling a MC electron trajectory simulation with a 3D Poisson-2D Schrödinger solver, and accounting for the modified acoustic phonon, optical phonon, and surface roughness scattering mechanisms. We apply the simulator to investigate the effect of the overlap factor, scattering mechanisms, material and geometrical properties on the mobility in silicon nanowire field-effect transistors (NWTs). This paper emphasizes the importance of using 1D models that include correctly quantum confinement and allow for a reliable prediction of the performance of NWTs at the scaling limits. Our simulator is a valuable tool for providing optimal designs for ultra-scaled NWTs, in terms of performance and reliability.