Border traps in 6H-SiC metal-oxide-semiconductor capacitors investigated by the thermally-stimulated current technique

We demonstrate the usefulness of the thermally-stimulated current (TSC) technique for investigating shallow interface state defects in silicon carbide metal-oxide-semiconductor (MOS) structures. For dry oxides, low-temperature TSC measurements reveal a high density of near-interfacial oxide traps (border traps) close to the band edges of 6H-SiC. Furthermore we find that annealing the SiC/SiO₂ interface in pyrogenic steam at 950 °C (reoxidation) essentially reduces the density of deep interface states, while it increases the density of shallow states. Our results agree with observations of the appearance of a negative oxide charge in reoxidized MOS capacitors and the corresponding increase of the threshold voltage in n channel metal-oxide-semiconductor field-effect transistors.