Electron capture and emission at interface states in As-oxidized and NO-annealed SiO2/4H-SiC

The electrical and physical properties of silicon carbide (SiC) and its ability to form insulating SiO₂ layers by thermal oxidation make it a promising material for high power, high-temperature, and high-frequency metal-oxide-semiconductor field effect transistors (MOSFETs). However, the development of 4H-SiC MOSFETs has been hindered by the high-density of interface states (D_it) at the SiO₂/4H-SiC interface and a reduced electron mobility of <10cm²/Vs in n-channel inversion layers. Interfacial nitridation via post-oxidation annealing in NO results in the incorporation of about a monolayer of N (~10¹⁵cm^-2) at or near the interface and reduces D_it near the conduction band-edge of 4H-SiC by almost an order of magnitude, leading to a significantly improved effective channel mobility in n-channel 4H-SiC MOSFETs. While nitridation has been established as the most efficient oxide processing scheme for SiC devices, the N related trap passivation mechanism and the electronic nature of residual traps at nitrided SiO₂/4H-SiC interfaces remains unclear. Here we present new insights on the capture and emission properties of interface traps from constant capacitance deep level spectroscopy (CCDLTS) measurements.