Trap assisted conduction in high K dielectric capacitors on 4H-SiC

The characteristic of trap assisted conduction and interface states for a Pd/TiO2/SiO2/SiC structure has been investigated at temperatures up to 500 degrees C. Thermally oxidized Ti/SiO2 gate capacitors fabricated by dry oxidation in O-2 were studied. The electrical measurements show the current conduction through this capacitor structure is controlled by a trap assisted conduction mechanism at low bias and the barrier height (phi(A)) between the metal and the TiO2 was extracted. The current density in the dielectric stacks is also shown to be strongly temperature dependent. The results demonstrate that the formation of a charge dipole under the Pd contact is responsible for barrier height and not any changes in the behaviour of the TiO2 film itself, such as a change in concentration of trapping centres. The reported results indicate electron trapping property across the SiO2 layer is consistent with fitting experimental results to the trap assisted conduction model.