Native point defects and carbon clusters in 4H-SiC: A hybrid functional study

TL;DR

This study uses hybrid functional first-principles calculations to analyze native point defects and carbon clusters in 4H-SiC, revealing their formation energies, charge states, and stability under different doping conditions.

Contribution

It provides a comprehensive computational analysis of defect energetics and configurations in 4H-SiC, improving understanding of defect behavior with a reliable hybrid functional approach.

Findings

Neutral Si antisites are energetically favorable in intrinsic conditions.

Negatively charged Si vacancies and positively charged Si interstitials dominate under n- and p-type doping.

A di-carbon antisite is more stable than a C-split interstitial.

Abstract

We report first-principles calculations that clarify the formation energies and charge transition levels of native point defects and carbon clusters in the 4H polytype of silicon carbide (4H-SiC) under a carbon-rich condition. We applied a hybrid functional that reproduces the experimental bandgap of SiC well and offers reliable defect properties. For point defects, we investigated single vacancies, antisites, and interstitials of Si and C on relevant sites. For carbon clusters, we systematically introduced two additional C atoms into the perfect 4H-SiC lattice with and without removing Si atoms and performed structural optimization to identify stable defect configurations. We found that neutral Si antisites are energetically favorable among Si-point defects in a wide range of the Fermi level position around the intrinsic regime, whereas negatively-charged Si vacancies and a positively-charged Si interstitial on a site surrounded by three Si and three C atoms become favorable under n- and p-type conditions, respectively. For C-point defects, neutral C antisites are favorable under intrinsic and n-type conditions, whereas positively-charged C vacancies become favorable under p-type conditions. We also found that a di-carbon antisite is more favorable than a C-split interstitial, which is the most stable form of single C interstitials.