N-channel field-effect mobility inversely proportional to the interface state density at the conduction band edges of SiO2/4H-SiC interfaces

摘要

We investigated the effects of the interface state density (D IT) at the interfaces between SiO2 and the Si-, C-, and a-faces of 4H-SiC in n-channel metal-oxide-semiconductor field-effect transistors that were subjected to dryitridation and pyrogenic/hydrotreatment processes. The interface state density over a very shallow range from the conduction band edge (0.00 eV < E C ? E T) was evaluated on the basis of the subthreshold slope deterioration at low temperatures (11 K < T). The interface state density continued to increase toward E C, and D IT at E C was significantly higher than the value at the conventionally evaluated energies (E C ? E T = 0.1–0.3 eV). The peak field-effect mobility at 300 K was clearly inversely proportional to D IT at 0.00 eV, regardless of the crystal faces and the oxidation/annealing processes.