Carbon antisite clusters in SiC: a possible pathway to the D_{II} center

TL;DR

This study suggests that carbon antisite clusters in silicon carbide could be the microscopic origin of the D_{II} luminescence center, supported by ab-initio vibrational spectra matching experimental features.

Contribution

It identifies carbon antisite clusters as a plausible structural model for the D_{II} center in SiC based on vibrational spectra calculations.

Findings

Vibrational modes of carbon antisite clusters match D_{II} spectra

Clusters have high binding energies indicating thermal stability

The (C_{2})_{Si} di-carbon antisite is a key component

Abstract

The photoluminescence center D_{II} is a persistent intrinsic defect which is common in all SiC polytypes. Its fingerprints are the characteristic phonon replicas in luminescence spectra. We perform ab-initio calculations of vibrational spectra for various defect complexes and find that carbon antisite clusters exhibit vibrational modes in the frequency range of the D_{II} spectrum. The clusters possess very high binding energies which guarantee their thermal stability--a known feature of the D_{II} center. The di-carbon antisite (C_{2})_{Si} (two carbon atoms sharing a silicon site) is an important building block of these clusters.