Electron Mobility in Silicon Nanowires (original) (raw)
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Journal of Applied Physics, 2008
We investigate the effects of electron and acoustic-phonon confinement on the low-field electron mobility of thin square silicon nanowires (SiNWs) that are surrounded by SiO2 and gated. We employ a self-consistent Poisson-Schrödinger-Monte Carlo solver that accounts for scattering due to acoustic phonons (confined and bulk), intervalley phonons, and the Si/SiO2 surface roughness. The wires considered have cross sections between 3 × 3 nm 2 and 8 × 8 nm 2 . For larger wires, as expected, the dependence of the mobility on the transverse field from the gate is pronounced. At low transverse fields, where phonon scattering dominates, scattering from confined acoustic phonons results in about a 10% decrease of the mobility with respect to the bulk phonon approximation. As the wire cross-section decreases, the electron mobility drops because the detrimental increase in both electron-acoustic phonon and electron-surface roughness scattering rates overshadows the beneficial volume inversion and subband modulation. For wires thinner than 5 × 5 nm 2 , surface roughness scattering dominates regardless of the transverse field applied and leads to a monotonic decrease of the electron mobility with decreasing SiNWs cross section.
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
Electronic Properties of Silicon Nanowires: Confined Phonons and Surface Roughness
2006 Sixth IEEE Conference on Nanotechnology, 2006
Electron mobility in narrow, rectangular silicon nanowires is calculated using a Schrödinger-Monte-Carlo-Poisson transport simulator. Mobility lowering due to the carrier scattering with confined phonons in narrow wires and the influence of surface roughness within Ando's model are investigated.
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.
Carrier-phonon interaction in small cross-sectional silicon nanowires
Journal of Applied Physics, 2008
Using first-order perturbation theory and deformation potential approximation, the interaction of electrons and holes with acoustic and optical phonons is investigated in silicon nanowires ͑SiNWs͒ with different diameters and crystallographic axis orientations. The electronic band structures for ͓110͔ and ͓100͔ SiNWs are obtained from a sp 3 d 5 s ء tight-binding scheme, while a continuum model is assumed for phonon dispersion. The influence of confined and bulk phonons on carrier transport is investigated.
Phys Rev B, 2011
A simulation framework that couples atomistic electronic structures to Boltzmann transport formalism is developed and applied to calculate the transport characteristics of thin silicon nanowires (NWs) up to 12 nm in diameter. The sp3d5s*-spin-orbit-coupled atomistic tight-binding model is used for the electronic structure calculation. Linearized Boltzmann transport theory is applied, including carrier scattering by phonons, surface roughness (SRS), and impurities. We present a comprehensive investigation of the low-field mobility in silicon NWs considering i) n- and p-type NWs, ii) [100], [110], and [111] transport orientations, and iii) diameters from D = 12 nm (electronically almost bulk-like) down to D = 3 nm (ultra-scaled). The simulation results display strong variations in the characteristics of the different NW types. For n-type NWs, phonon scattering and SRS become stronger as the diameter is reduced and drastically degrade the mobility by up to an order of magnitude depending on the orientation. For the [111] and [110] p-type NWs, on the other hand, large mobility enhancements (on the order of ˜4×) can be achieved as the diameter scales down to D = 3 nm. This enhancement originates from the increase in the subband curvatures as the diameter is scaled. It overcompensates for the mobility reduction caused by SRS in narrow NWs and offers an advantage with diameter scaling. Our results may provide understanding of recent experimental measurements, as well as guidance in the design of NW channel devices with improved transport properties.
Strong anisotropy and diameter effects on the low-field mobility of silicon nanowires
2011 International Conference on Simulation of Semiconductor Processes and Devices, 2011
We describe a method to couple the sp 3 d 5 s * -spin-orbitcoupled (SO) atomistic tight-binding (TB) model and linearized Boltzmann transport theory for the calculation of low-field mobility in Si nanowires (NWs). We consider scattering mechanisms due to phonons and surface roughness. We perform a simulation study of the low-field mobility in n-type and p-type Si NWs of diameters from 3nm to 12nm, in the [100], [110] and [111] transport orientations. We find that the NW mobility is a strong function of orientation and diameter. This is a consequence of the large variations in the electronic structure with geometry and quantization. Especially in the case of p-type [111] and [110] NWs, large phonon-limited mobility improvements with diameter scaling are observed.
Electron Transport in Si Nanowires
Journal of Physics: Conference Series, 2006
We investigate electron transport in silicon nanowires taking into account acoustic, non-polar optical phonons and surface/interface roughness scattering. We find that at very high transverse fields the reduced density of final states to which the carriers can scatter into gives rise to a reduced influence of interface-roughness scattering, which is promising result from a fabrication point of view.
Journal of Applied Physics, 2007
We present a theoretical study of electron mobility in cylindrical gated silicon nanowires at 300 K based on the Kubo-Greenwood formula and the self-consistent solution of the Schrödinger and Poisson equations. A rigorous surface roughness scattering model is derived, which takes into account the roughness-induced fluctuation of the subband wave function, of the electron charge, and of the interface polarization charge. Dielectric screening of the scattering potential is modeled within the random phase approximation, wherein a generalized dielectric function for a multi-subband quasi-one-dimensional electron gas system is derived accounting for the presence of the gate electrode and the mismatch of the dielectric constant between the semiconductor and gate insulator. A nonparabolic correction method is also presented, which is applied to the calculation of the density of states, the matrix element of the scattering potential, and the generalized Lindhard function. The Coulomb scattering due to the fixed interface charge and the intra-and intervalley phonon scattering are included in the mobility calculation in addition to the surface roughness scattering. Using these models, we study the low-field electron mobility and its dependence on the silicon body diameter, effective field, dielectric constant, and gate insulator thickness.
Nano Letters, 2008
Utilizing sp3d5s* tight-binding band structure and wave functions for electrons and holes we show that acoustic phonon limited hole mobility in [110] grown silicon nanowires (SiNWs) is greater than electron mobility. The room temperature acoustically limited hole mobility for the SiNWs considered can be as high as 2500 cm 2 /V s, which is nearly three times larger than the bulk acoustically limited silicon hole mobility.