Low-Temperature Electron Transport in [110] and [100] Silicon Nanowires: A DFT - Monte Carlo study

TL;DR

This study investigates low-temperature electron transport in silicon nanowires using DFT and Monte Carlo methods, revealing increased drift velocities and pronounced streaming electron motion at low temperatures.

Contribution

It combines DFT, tight-binding, and Monte Carlo methods to analyze low-temperature electron transport in [110] and [100] silicon nanowires, highlighting differences in drift velocities.

Findings

Electron drift velocity doubles at low temperature compared to room temperature.

[110] nanowires exhibit 50% higher drift velocity than [100] nanowires.

Pronounced streaming electron motion observed at low temperature.

Abstract

The effects of very low temperature on the electron transport in a [110] and [100] axially aligned unstrained silicon nanowires (SiNWs) are investigated. A combination of semi-empirical 10-orbital tight-binding method, density functional theory (DFT), and Ensemble Monte Carlo (EMC) methods are used. Both acoustic and optical phonons are included in the electron-phonon scattering rate calculations covering both intra-subband and inter-subband events. A comparison with room temperature (300 K) characteristics shows that for both nanowires, the average electron steady-state drift velocity increases at least 2 times at relatively moderate electric fields and lower temperatures. Furthermore, the average drift velocity in [110] nanowires is 50 percent more than that of [100] nanowires, explained by the difference in their conduction subband effective mass. Transient average electron velocity suggests that there is a pronounced streaming electron motion at low temperature which is attributed to the reduced electron-phonon scattering rates.