Charged impurity scattering and mobility in gated silicon nanowires

Abstract

We study the effects of charged impurity scattering on the electronic transport properties of <110>-oriented Si nanowires in a gate-all-around geometry, where the impurity potential is screened by the gate, gate oxide and conduction band electrons. The electronic structure of the doped nanowires is calculated with a tight-binding method and the transport properties with a Landauer-Buttiker Green functions approach and the linearized Boltzmann transport equation (LBTE) in the first Born approximation. Based on our numerical results we argue that: (1) There are large differences between Phosphorous (P) and Boron (B) doped systems, acceptors behaving as tunnel barriers for the electrons, while donors give rise to Fano resonances in the transmission. (2) As a consequence, the mobility is much larger in P- than in B-doped nanowires at low carrier density, but can be larger in B-doped nanowires at high carrier density. (3) The resistance of a single impurity is strongly dependent on its radial position in the nanowire, especially for acceptors. (4) As a result of subband structure and screening effects, the impurity-limited mobility can be larger in thin nanowires embedded in HfO2 than in bulk Si. Acceptors might, however, strongly hinder the flow of electrons in thin nanowires embedded in SiO2. (5) The perturbative LBTE largely fails to predict the correct mobilities in quantum-confined nanowires.

Submitted to Phys. rev. B

References in corpus (5)

• A knitting algorithm for calculating Green functions in quantum systems
• Scaling theory put into practice: first-principles modeling of transport in doped silicon nanowires
• Electronic transport in Si nanowires: Role of bulk and surface disorder
• Significant enhancement of hole mobility in [110] silicon nanowires compared to electrons and bulk silicon
• Green's function approach to transport through a gate-all-around Si nanowire under impurity scattering