Systematic investigation on in-plane anisotropy of surface and buried channel mobility of metal-oxide-semiconductor field-effect-transistors on Si-, a-, and m-face 4H-SiC

We have systematically investigated the channel mobility of the 4H-SiC MOSFETs with surface and buried channels in different directions on Si-, a-, and m-faces. We have found that, on a- and m-faces, the in-plane anisotropy of the surface channel mobility is different from that of the buried channel mobility. It has been demonstrated that this anomalous anisotropic behavior can be observed regardless of the gate oxide processes. These results suggest that the dependence of scattering mechanisms or effective masses of carriers on crystal orientations may be modulated near the oxide/SiC interface.