Effect of nitric oxide annealing on the interface trap densities near the band edges in the 4H polytype of silicon carbide

Results of capacitance–voltage measurements are reported for metal–oxide–semiconductor capacitors fabricated using the 4H polytype of silicon carbide doped with either nitrogen (n) or aluminum (p). Annealing in nitric oxide after a standard oxidation/reoxidation process results in a slight increase in the defect state density in the lower portion of the band gap for $\mathrm{p-}\mathrm{SiC}$ and a significant decrease in the density of states in the upper half of the gap for $\mathrm{n-}\mathrm{SiC}.$ Theoretical calculations provide an explanation for these results in terms of N passivating C and C clusters at the oxide–semiconductor interface.