TEMPERATURE-DEPENDENCE OF FOWLER-NORDHEIM CURRENT IN 6H-SIC AND 4H-SIC MOS CAPACITORS

This work reports on Fowler-Nordheim (F-N) injection studies on n-type 6H-SiC and 4H-SiC MOS systems under positive gate bias from 25 to 325 degrees C. At a given temperature and electric field, the current den sity in the 4H-SiC MOS system is about five times higher than that in 6H-SiC due to the smaller effective barrier height for the JH-SIC MOS system as compared to 6H-SiC. The reduction of the effective barrier h eight with temperature, particularly in 4H-SiC, raises serious concern s about the long-term reliability of gate oxides in SIC. It is conclud ed that the maximum practical values of electric field in the 4H-SiC M OS system under positive gate bias and high junction temperature shoul d be reduced to below the values used in the Si MOS system.