Systematic Study of Electron Localization in an Amorphous Semiconductor

TL;DR

This study systematically examines how basis set size, density functional choice, and spin polarization affect electron localization in amorphous silicon, providing insights into defect state characterization.

Contribution

It offers a comprehensive analysis of electron localization dependence on computational parameters in amorphous silicon using first-principles methods.

Findings

Larger basis sets reduce defect state localization.

GGA enhances localization compared to LDA.

Spin localization aligns with experimental observations.

Abstract

We investigate the electronic structure of gap and band tail states in amorphous silicon. Starting with two 216-atom models of amorphous silicon with defect concentration close to the experiments, we systematically study the dependence of electron localization on basis set, density functional and spin polarization using the first principles density functional code Siesta. We briefly compare three different schemes for characterizing localization: information entropy, inverse participation ratio and spatial variance. Our results show that to accurately describe defect structures within self consistent density functional theory, a rich basis set is necessary. Our study revealed that the localization of the wave function associated with the defect states decreases with larger basis sets and there is some enhancement of localization from GGA relative to LDA. Spin localization results obtained via LSDA calculations, are in reasonable agreement with experiment and with previous LSDA calculations on a-Si:H models.