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

We investigated the effects of the interface state density (DIT) 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 dry/nitridation and pyrogenic/hydrotreatment processes. The interface state density over a very shallow range from the conduction band edge (0.00 eV < EC − ET) was evaluated on the basis of the subthreshold slope deterioration at low temperatures (11 K < T). The interface state density continued to increase toward EC, and DIT at EC was significantly higher than the value at the conventionally evaluated energies (EC − ET = 0.1–0.3 eV). The peak field-effect mobility at 300 K was clearly inversely proportional to DIT at 0.00 eV, regardless of the crystal faces and the oxidation/annealing processes

Behavior of Leakage Current in SiC MOS Capacitors Introduced by Heavy Ions

Gradual increase in leakage current introduced by heavy ions irradiation was observed for silicon carbide metal-oxide-semiconductor (SiC MOS) capacitors under the negative bias voltage condition. In contrast, abrupt increase was observed for positive biased condition as previously observed for Si MOS devices. It was identified that the degradation sites introduced under negative bias have a rectifying I–V characteristic, which were too small to cause a clear shift of the C–V curve. It was inferred that the hetero junction formed in SiC MOS capacitors was the key structure for suppressing catastrophic failures mode observed in Si MOS structures. 　Nuclear & Space Radiation Effects Conference 2020( NSREC 2020