Low-temperature electrical measurements and photon-stimulated electron tunnelling experiments revealed the presence of a high density of interface states at about 0.1eV below the conduction band of 4H-type material, at its interface with thermally grown SiO2. These states, which were related to defects in the near-interfacial oxide layer, trapped a considerable number of electrons from the SiC and were suggested to be responsible for a severe degradation of the electron mobility in the surface channel of 4H-SiC/SiO2 devices. The negative effect of the defects could be minimized by using SiC modifications (6H, 15R, 3C) which had a larger conduction-band offset than did 4H-SiC.

Shallow Electron Traps at the 4H-SiC/SiO2 Interface V.V.Afanasev, A.Stesmans, M.Bassler, G.Pensl, M.J.Schulz: Applied Physics Letters, 2000, 76[3], 336-8