Simulation of the impact of ionized impurity scattering on the total mobility in si nanowire transistors

Toufik Sadi*, Cristina Medina-Bailon, Mihail Nedjalkov, Jaehyun Lee, Oves Badami, Salim Berrada, Hamilton Carrillo-Nunez, Vihar Georgiev, Siegfried Selberherr, Asen Asenov

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

12 Citations (Scopus)
108 Downloads (Pure)


Nanowire transistors (NWTs) are being considered as possible candidates for replacing FinFETs, especially for CMOS scaling beyond the 5-nm node, due to their better electrostatic integrity. Hence, there is an urgent need to develop reliable simulation methods to provide deeper insight into NWTs' physics and operation, and unlock the devices' technological potential. One simulation approach that delivers reliable mobility values at low-field near-equilibrium conditions is the combination of the quantum confinement effects with the semi-classical Boltzmann transport equation, solved within the relaxation time approximation adopting the Kubo-Greenwood (KG) formalism, as implemented in this work. We consider the most relevant scattering mechanisms governing intraband and multi-subband transitions in NWTs, including phonon, surface roughness and ionized impurity scattering, whose rates have been calculated directly from the Fermi's Golden rule. In this paper, we couple multi-slice Poisson-Schrödinger solutions to the KG method to analyze the impact of various scattering mechanisms on the mobility of small diameter nanowire transistors. As demonstrated here, phonon and surface roughness scattering are strong mobility-limiting mechanisms in NWTs. However, scattering from ionized impurities has proved to be another important mobility-limiting mechanism, being mandatory for inclusion when simulating realistic and doped nanostructures, due to the short range Coulomb interaction with the carriers. We also illustrate the impact of the nanowire geometry, highlighting the advantage of using circular over square cross section shapes.

Original languageEnglish
Article number124
Issue number1
Publication statusPublished - 2 Jan 2019
MoE publication typeA1 Journal article-refereed


  • Charge transport
  • Kubo-Greenwood formalism
  • Nanowire field-effect transistors
  • One-dimensional multi-subband scattering models
  • Schrödinger-poisson solvers
  • Silicon nanomaterials

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