Effect Of 4H-SiC Surface Morphology On Lnterfacial Electricat Properties Of 2D-MoS₂/3D-SiC Heterojunction

The combination of 3D-SiC and 2D-MoS₂,combined with the high p-type conductivity and low turn-on voltage of 2D-MoS₂,and the wide band gap and high breakdown electric field of SiC,makes the heterojunctions show potential advantages in the field of photodetectors and pho-tocatalysis.The electronic structure of 2D materials directly depends on the surface structure of the substrate material.As the substrate material for direct growth of MoS₂,the surface morphol-ogy of SiC plays a key role in the electrical properties of MoS₂ and the MoS₂/SiC heterojunction interface.Therefore,theoretically exploring how the different surfaces of SiC affect the interface and the electrical properties of MoS₂ has practical significance in the application of 3D-SiC/2D-MoS₂ heterojunction devices and the epitaxy of high-quality MoS₂ on SiC substrates.In this re-search work,first-principles density functional theory(DFT)calculations were performed on the 4H-SiC and 2D-MoS₂ heterojunction interfaces with different surface morphologies,the interfa-cial electrical properties of 2D-MoS₂ and 4H-SiC heterostructures formed by ideal surface,(?)reconstructed surface,H-passivated surface and surface with vacancy defects and im-purity atoms were studied respectively.The main conclusions are as follows:1.The dangling bonds of Si atoms on the ideal SiC surface and S atoms of MoS₂ form stable? covalent bonds at the interface,which will deform the band structure of MoS₂ and increase the effective mass of electrons.2.In the heterojunction interface formed by the SiC(?)reconstructed surface and MoS₂ in three different stacking configurations,energy band calculations show that in two of the interface configurations,intermediate states are introduced in the forbidden band of MoS₂ and the surface state energy levels of SiC reconstructed surface are broadened towards the conduction band,while in the other interface configuration,the surface reconfigured Si atoms form covalent bonds with S atoms and the conduction band of MoS₂ and SiC surface state energy level under-goes degenerate.3.The H-passivated SiC and MoS₂ form a van der Waals heterojunction,and the heterojunction forms a type-? band structure.The heterostructure is controlled by the vertical electric field,the conduction band offset and the valence band offset increases with the increase of the positive electric field.4.Through the quantitative analysis of the interface binding energy,it is found that the in-terface with N impurity atoms is the most stable,the interface with P impurity atoms is the most unstable,At the same time,the energy band calculation shows that the N,P impurity atom intro-duces a highly localized electronic state in the interface forbidden band,while the surface Al impurity atom does not introduce any intermediate state energy level in the forbidden band.5.The existence of C vacancy defects on the SiC surface leads to the rearrangement of sur-face Si atoms,introducing a defect state at the position of the interface forbidden band close to the conduction band,and at the same time,it also makes MoS₂ generate a new intermediate state energy level in the forbidden band,while the surface of SiC with Si vacancy defects introduce corresponding defect energy levels in the interface forbidden band near the valence band.