Extended Huckel theory for bandstructure, chemistry, and transport. II. Silicon

TL;DR

This paper develops transferable semi-empirical Extended Huckel Theory parameters for silicon, accurately modeling its electronic structure, surfaces, and nanowires, enabling improved quantum transport simulations.

Contribution

It introduces optimized EHT parameters for silicon that match experimental bandstructure data and are applicable to various environments and nanostructures.

Findings

Accurately reproduces silicon bandstructure and effective masses.

Successfully models surface states and reconstructions.

Demonstrates applicability to silicon nanowires and surface passivation.

Abstract

In this second paper, we develop transferable semi-empirical parameters for the technologically important material, silicon, using Extended Huckel Theory (EHT) to calculate its electronic structure. The EHT-parameters areoptimized to experimental target values of the band dispersion of bulk-silicon. We obtain a very good quantitative match to the bandstructure characteristics such as bandedges and effective masses, which are competitive with the values obtained within an $sp^3 d^5 s^*$ orthogonal-tight binding model for silicon. The transferability of the parameters is investigated applying them to different physical and chemical environments by calculating the bandstructure of two reconstructed surfaces with different orientations: Si(100) (2x1) and Si(111) (2x1). The reproduced $\pi$- and $\pi^*$-surface bands agree in part quantitatively with DFT-GW calculations and PES/IPES experiments demonstrating their robustness to environmental changes. We further apply the silicon parameters to describe the 1D band dispersion of a unrelaxed rectangular silicon nanowire (SiNW) and demonstrate the EHT-approach of surface passivation using hydrogen. Our EHT-parameters thus provide a quantitative model of bulk-silicon and silicon-based materials such as contacts and surfaces, which are essential ingredients towards a quantitative quantum transport simulation through silicon-based heterostructures.