CHARGE TRAPPING IN DRY AND WET OXIDES ON N-TYPE 6H-SIC STUDIED BY FOWLER-NORDHEIM CHARGE INJECTION

Metal-oxide-semiconductor capacitors fabricated by dry and wet oxidati on at 1150 degrees C of n-type 6H-SiC exhibit a drastic negative charg ing during Fowler-Nordheim charge injection. This charging strongly de pends on the fabrication conditions of the samples. The densities of i nterface states and oxide charges can be significantly reduced by a po stoxidation anneal in Ar for as long as 60 min. A large part of the ch arge appears to be trapped at the interface. These charges are release d from the traps by illumination at photon energies between 2 and 4 eV or by annealing below 300 degrees C. During charge injection interfac e states are created near the conduction band edge. Their density is s trongly reduced by annealing at 150 degrees C. For the oxide charging we find capture cross sections in the range of 10(-15)-10(-17) cm(-2). In unannealed wet oxidized samples the traps exhibit properties simil ar to those of water-related traps in SiO2 on Si. (C) 1996 American In stitute of Physics.