The effect of defects and their passivation on the density of states of the 4H-silicon-carbide/silicon-dioxide interface

The 4H-SiC(0001)/SiO2 interface has a variety of likely defects as reported in the literature. We investigate the defects at the SiC side of the interface using density functional theory. We also investigate the effects of passivating these states. The defects studied include a single carbon interstitial, a carbon pair interstitial, and a silicon vacancy at the interface. Density functional theory has been employed to calculate the total and projected density of states (pDOS) and the energy levels of the defects. The results of our calculations indicate that a carbon interstitial and a pair of carbons give rise to traps near the conduction band and valence band. The silicon vacancy gives rise to traps that are closer to the valence band. The effects of hydrogen and nitrogen passivation on the defect energy levels have been investigated. Our studies indicate that hydrogen and nitrogen passivation can eliminate states near the conduction and valence bands, although in some cases they may introduce levels in the midgap.