• Background

Silicon carbide (SiC) is wide gap semiconductor and  the most promising material for power electric devices. One of the advantage of SiC is oxide layer can be grown by conventional thermal oxidation. However, SiC MOS devices of current technology are far form satisfactory owing to large defect levels. Presence of such defects causes problems such as low channel mobility and reliability.

Carbon atoms which are bi-products of thermal oxidation are accumulated near the SiC/SiO2 interfaces. They are considered as one of origin of such large defect levels. For this problem, we performed first-principles calculations to 

• Distribution of C related defects levels

We investigated C related defect levels using first-principles calculations with hybrid density functional. In this paper, we considered Si2>C=O (carbonyl group) and Si2>C=C<Si2 (C2 dimer) defects which are suggested have defect levels near the conduction band bottom of SiC. We introduced the defects more than 10 different configurations for both the Si2>C=O and Si2>C=C<Si2 structures.

We found that the C related defects levels have wide distribution depending on those local structures. For Si2>C=O structure defect, the energetic positions of defect levels depend on the interatomic distance between O and other Si. For the Si2>C=C<Si2 structure, the defect level positions depend on the dihedral angle along Si-C-C-Si. 

See T. Kaneko et al., Appl. Phys. Express 11, 011302 (2018).

• Proposal of passivation of C=C defect

In this paper, we considered the passivation of Si2>C=C<Si2 defect by reaction with H2 and F2.

See N. Tajima, T. Kaneko et al., Jpn. J. Appl. Phys. 57, 04FR09 (2018).

• Model construction on a- and m-faces of 4H-SiC

Recently, SiC MOS devices on a- and m-face attract much interest owing to the higher mobilities compared with that for Si-face. In this paper, we proposed dangling bond free abrupt interface model of 4H-SiC/SiO2 on a- and m-faces of 4H-SiC. 

See T. Kaneko et al., Appl. Phys. Express 11, 101304 (2018).