4H-SiC Surface Structures and Oxidation Mechanism Revealed by Using First-Principles and Classical Molecular Dynamics Simulations

Abstract

The 4H-SiC(000-1)C and (0001)Si surface reconstructed structures and the oxidation processes of these surfaces are investigated using a first-principles calculation method. The most stable reconstructed 4H-SiC(000-1)C and (0001)Si surfaces have p-bonded chains. In the topmost SiC bilayer, half of Si and C atoms exchange their positions and C-C or Si-Si bonds formed densely below the surfaces. When we place a SiO2 layer on the p-bonded chain (000-1)C surface, C-C bonds are formed more densely below the interface. We simulate a sequence of O2 molecules arrivals at an interface of tridymite-phase-SiO2 and 4H-SiC(000-1)C. Dissociated O atoms at the interface tended to make bonds with Si atoms. The C-C bonds in the SiC substrate break easily and a local C surface occasionally appears. We have examined how the surface structure changes through an O2 molecule exposure by using a classical molecular dynamics simulation program and confirmed the formation of C-C bonds below the surface and the interface.

Hybrid density functional analysis of distribution of carbon-related defect levels at 4H-SiC(0001)/SiO2 interface

“…Theoretical studies using first-principles calculations have been carried out by several authors [6][7][8][9][10][11][12][13][14][15][16][17] to address this issue. Knaup et al reported that a carbon interstitial defect [carbonyl group-like structure; see Fig.…”

“…They suggested that the carbon atoms emitted from SiC substrate tend to form carbonyl groups or C clusters containing C=C double bonds. 15) We need to understand the electronic structures of these defects to verify whether they are the origin of the large D it and NIT. Because the oxide layer of the SiC=SiO 2 interface is amorphous, the C=O and C=C defects can have structural variations, which may shift the energetic position of the corresponding defect level.…”