Structural stability and energy levels of carbon-related defects in amorphous SiO$_2$ and its interface with SiC

TL;DR

This study uses density-functional calculations to identify stable carbon-related defects in amorphous SiO$_2$ and their energy levels, revealing their potential role as carrier traps near the SiC interface.

Contribution

It systematically clarifies the stable forms and energy levels of carbon-related defects in amorphous SiO$_2$ considering interface effects, using melt-quench molecular dynamics.

Findings

CO$_2$ and CO are abundant and inactive far from the interface.

Near the interface, carbon clustering occurs and specific defects induce energy levels near the conduction band.

Defects near the interface may act as carrier traps.

Abstract

We report the density-functional calculations that systematically clarify the stable forms of carbon-related defects and their energy levels in amorphous SiO$_2$ using the melt-quench technique in molecular dynamics. Considering the position dependence of the O chemical potential near and far from the SiC/SiO$_2$ interface, we determine the most abundant forms of carbon-related defects: Far from the interface, the CO$_2$ or CO in the internal space in SiO$_2$ is abundant and they are electronically inactive; near the interface, the carbon clustering is likely and a particular mono-carbon defect and a di-carbon defect induce energy levels near the SiC conduction-band bottom, thus being candidates for the carrier traps.