Ideal phonon-scattering-limited mobility in inversion channels of 4H-SiC(0001) MOSFETs with ultralow net doping concentrations

The phonon-limited mobility in 4H-silicon carbide (SiC) inversion channels was precisely evaluated by employing ultralow net doping concentrations. The measured mobility in the inversion channels of these samples was comparable to the electron mobility in bulk 4H-SiC, and the temperature dependence indicated that the mobility can be ascribed to phonon-scattering-limited mobility. The strong dependence of the mobility on the net doping concentration cannot be explained by Coulomb scattering by dopant impurities. This indicates the existence of scattering origins at the SiO2/SiC interface. Comparison of dry oxidized samples and samples subjected to postoxidation annealing in nitric oxide revealed that the scattering origins were not attributable to trapped electrons at the SiO2/SiC interface states, although the nature of the scattering origins remains unclear.