Nitrogen-Induced Changes in the Electronic and Structural Properties of 4H-SiC (0001)/SiO2 Interfaces

Atom-level understanding of the emerging properties of interfaces introduced by chemical treatments is key to the development of electronic devices. Herein, changes in the 4H-SiC (0001)/SiO2 interfaces upon interfacial nitridation are analyzed in an array of realistic models that differ in composition and atomic arrangement using first-principles calculations within the density functional theory. In the absence of nitrogen, the electron density near the interface shows an unexpected reduction below the bulk oxide value. The introduction of nitrogen removes this feature by compensating the silicon density mismatch between SiC and SiO2 and stabilizes the interface through the relief of local strain. Both the density anomaly and its removal with nitridation are in agreement with recent X-ray reflectivity measurements. Moreover, analysis of the band structures shows alignments consistent with experimental reports that nitrogen, which favors bonding to Si rather than O atoms, creates interfacial states residing mainly near the valence band edge.