In this work the field effect mobility measured on lateral n-channel MOSFETs in 4H-SiC with Al implanted body was correlated with the interface trap density measured on MOS capacitors. The test devices were fabricated on samples subjected to different post implantation annealing conditions (ie with or without a protective carbon capping layer) and to an identical post-oxidation annealing in N 2 O. Despite the improved interfacial morphology, a reduction of the peak mobility (from 40 to 24 cm 2 V-1 s-1) was observed using the carbon capping layer. An increase in the density of interface traps was consistently found. Nanoscale measurements of the active dopant concentration in the SiC channel region by cross-sectional scanning capacitance microscopy showed an higher compensation of p-type SiC for the sample processed without the capping layer, which indicates a more efficient incorporation of nitrogen at the …