Observations of very fast electron traps at SiC/high-κ dielectric interfaces

Very fast interface traps have recently been suggested to be the main cause behind poor channel-carrier mobility in SiC metal-oxide-semiconductor field effect transistors. It has been hypothesized that the NI traps are defects located inside the SiO₂ dielectric with energy levels close to the SiC conduction band edge and the observed conductance spectroscopy signal is a result of electron tunneling to and from these defects. Using aluminum nitride and aluminum oxide as gate dielectrics instead of SiO₂, we detect NI traps at these SiC/dielectric interfaces as well. A detailed investigation of the NI trap density and behavior as a function of temperature is presented and discussed. Advanced scanning transmission electron microscopy in combination with electron energy loss spectroscopy reveals no SiO₂ at the interfaces. This strongly suggests that the NI traps are related to the surface region of the SiC rather than being a property of the gate dielectric.