In this paper, nanoscale resolution scanning capacitance microscopy (SCM) and local capacitance–voltage measurements were used to probe the interfacial donor concentration in SiO 2/4H–SiC systems annealed in N 2 O. Such nitrogen-based annealings are commonly employed to passivate SiO 2/SiC interface traps, and result both in the incorporation of N-related donors in SiC and in the increase of the mobility in the inversion layer in 4H–SiC MOS-devices. From our SCM measurements, a spatially inhomogeneous donor distribution was observed in the SiO 2/4H–SiC system subjected to N 2 O annealing. Hence, the effect of a phosphorus implantation before the oxide deposition and N 2 O annealing was also evaluated. In this case, besides an increased average donor concentration, an improvement of the lateral homogeneity of the active doping was also detected. The possible implications of such a pre …