Study On Thermal-mechanical Characteristics Of Graphene/Silicon Carbide Heterogeneous Interface In Power Devices

Limited by the characteristics of silicon materials,the development space of silicon based devices is limited.The wide band gap semiconductor devices represented by silicon carbide are suitable for high temperature,high pressure and high frequency occasions,which contribute to the improvement of the efficiency and power density of electronic systems.Aiming at the application of the third-generation semiconductor material silicon carbide in the heterostructure of power devices,the thermal-mechanical characteristics of silicon carbide/graphene heterogeneous interface under the influence of different factors were comparatively studied by molecular dynamics method.The main conclusions are as follows:(1)The sandwich graphene/silicon carbide heterogeneous interface was constructed,and the effects of different temperature,size and defect rate on the interfacial thermal conductivity were studied by non-equilibrium molecular dynamics method.The results show that the interfacial thermal conductivity increases with the increase of temperature,but the heterogeneous interfacial thermal conductivity of covalent bond is higher than that of van der Waals force.The interfacial thermal conductivity of heterogeneous interface decreases with the increase of silicon carbide layers.When the number of layers increases from 10 to 20,the interfacial thermal conductivity decreases by 30.5%.The introduction of vacancy defects can effectively improve the interfacial thermal conductivity.The interfacial thermal conductivity first increases and then decreases with the increase of defect rate of silicon carbide and graphene.At 300 K,the interfacial thermal conductivity reaches the maximum when the defect rates of Si C and graphene are 20% and 35%,respectively.(2)Single-layer graphene/silicon carbide heterogeneous interface was constructed,and the effects of four kinds of graphene intrinsic defects: point defects,carbon adatoms defects,single vacancy defects and multiple vacancies defects on thermal conductivity were studied.It is found that the thermal conductivity decreases with the introduction of four intrinsic defects.Among them,single vacancy defects has the greatest influence on thermal conductivity and phonon state density of graphene,and the degree of influence of carbon adatoms defects on thermal conductivity is related to the direction.The influence of multiple vacancies defects on thermal conductivity is similar to that of single vacancy,while point defects have little influence on thermal conductivity.In addition,The effect of surface hydrogenated monolayer graphene on thermal conductivity of Si C nanoribbons was also studied.In zigzag and armchair directions,the thermal conductivity increases when the hydrogenation rate increases from 0% to 1%,and then decreases with the increase of hydrogenation rate,and the thermal conductivity increases by 4.8% and 7.5%when the hydrogenation rate is 1%,respectively.(3)Based on the molecular dynamics method,three different models were studied by tensile simulation,Namely,the Young’s modulus and critical stress of silicon carbide nanoribbons,silicon carbide/graphene,graphene/silicon carbide/graphene in different directions,and the mechanical properties of heterogeneous interfaces under different silicon carbide thicknesses,temperatures and strain rates are discussed.The results show that: Adding graphene layer on the surface of silicon carbide to form an interface can significantly improve the Young’s modulus and critical stress of silicon carbide.At 300 kelvin and the thickness of silicon carbide is 1.69 nm,the Young’s modulus of Gr/Si C and Gr/Si C/Gr interface structures in the armchair direction is increased by 49.2% and 128.2%respectively compared with Si C nano-film.Young’s modulus and critical stress decrease with the increase of silicon carbide thickness.The mechanical properties of the heterogeneous interface composed of graphene/silicon carbide will decrease with the increase of temperature.The increase of strain rate has little effect on Young’s modulus of heterogeneous interface,but it will slightly affect the critical stress.The research results of this paper show that the thermal-mechanical characteristics of heterogeneous interfaces can be regulated by size effect and defect engineering,which is beneficial to the design of micro-nano devices based on silicon carbide.