**4. Argon anneal**

Oxidation conditions and post-oxidation annealing (POA) can affect the trap density at the SiO2/4H-SiC interface. Both Ar anneal performed at growth temperature and re-oxidation at lower temperatures (e.g. 900 ◦C) have indeed proven to slightly reduce the amount of deep states [40, 129]. This can be explained by the removal of excess carbon without additional oxide formation, as corresponding atomic configurations yield defects populating interface states toward the middle of the gap. Since it does not reduce the density of levels close to the conduction band edge of 4H-SiC, Ar POA alone is not sufficient to enable efficient SiC devices. Nevertheless, it is typically used after thermal oxidation and before other annealing schemes.
