Investigation of Near-Interface Traps Generated by NO Direct Oxidation in C-face 4H-SiC Metal–Oxide–Semiconductor Structures

Characteristics of metal–oxide–semiconductor (MOS) capacitors and MOS field-effect transistors (MOSFETs) fabricated by direct oxidation of C-face 4H-SiC in NO were investigated. It was found from capacitance–voltage ( C – V ) measurements that interface state density ( D it ) at energies near the conduction band edge is reduced by direct oxidation of C-face 4H-SiC in NO, whereas this process generates near-interface traps (NITs) in the oxide. These traps capture channel mobile electrons and degrade the performance of MOSFETs. Both the interface states and the near-interface traps were reduced by unloading the samples at room temperature after the oxidation. It is important to reduce not only the interface states but also the near-interface traps to fabricate high-performance C-face 4H-SiC MOSFETs with nitrided gate oxide.