Optical lineshapes of the C-center in silicon from ab initio calculations: Interplay of localized modes and bulk phonons

TL;DR

This study uses first-principles DFT calculations to analyze the optical lineshapes of the C-center defect in silicon, revealing the roles of localized modes and bulk phonons in luminescence.

Contribution

It introduces a computational methodology to accurately model defect lineshapes in large supercells, combining localized and bulk vibrational effects.

Findings

Excellent agreement with experimental luminescence data

Confirmed the C-line in silicon originates from the neutral CiOi defect

Demonstrated the importance of both localized and bulk phonons in lineshape formation

Abstract

In this work, we present a first-principles density functional theory (DFT) computational investigation of the luminescence and absorption lineshapes associated with the neutral carbon-oxygen interstitial pair (CiOi) defect in silicon. We obtain the lineshapes of the defect in the dilute limit using a computational methodology that constructs dynamical matrices of supercells containing tens of thousands of atoms, utilizing systems directly accessible through DFT. Both perturbed bulk phonons and localized vibrations contribute to the phonon sideband. We achieve excellent agreement with experimental luminescence data. Our findings further reinforce the attribution of the well-known C-line in silicon to the neutral CiOi complex.