Charge trapping in dry and wet oxides on N-type 6H–SiC studied by Fowler–Nordheim charge injection

Abstract

Metal-oxide-semiconductor capacitors fabricated by dry and wet oxidation at 1150 °C of n-type 6H–SiC exhibit a drastic negative charging during Fowler–Nordheim charge injection. This charging strongly depends on the fabrication conditions of the samples. The densities of interface states and oxide charges can be significantly reduced by a postoxidation anneal in Ar for as long as 60 min. A large part of the charge appears to be trapped at the interface. These charges are released from the traps by illumination at photon energies between 2 and 4 eV or by annealing below 300 °C. During charge injection interface states are created near the conduction band edge. Their density is strongly reduced by annealing at 150 °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 similar to those of water-related traps in SiO2 on Si.