Simulation of Electrical and Thermal Properties of 4H-SiC Based on Molecular Dynamics

4H-SiC is widely used in high-temperature, high-frequency, and high-power electronic devices due to its unique crystal structure and excellent electrical properties. [1] As a common microstructure in materials, the existence of point defects will have a significant impact on the electronic properties, thermal conductivity and mechanical properties of materials. In this paper, the molecular dynamics method is used to simulate the microscopic morphology of the crystal in detail, and the relationship between point defects and the electronic properties such as band structure and density of states of the system is explored by constructing different defect forms, and the relationship between point defects and thermodynamic properties is further explored, and how the defects affect the electron transport and heat conduction characteristics of the materials, so as to provide a theoretical basis for optimizing the properties of materials. The crystal structure was constructed by Materials studio software, including the eigensystem, and three structural forms containing C vacancy defects and Si vacancy defects, and the images of energy bands and density of states in each system were calculated according to density functional theory. The results show that the intrinsic system of 4H-SiC is an indirect bandgap semiconductor with a band gap of 2.176 eV, and the band gap of 4H-SiC with C vacancy defect is 0.1795 eV, and the bandgap of 4H-SiC with Si vacancy defects is 0.5193eV. Compared with the eigensystem, the introduction of defects makes the band gap narrower, the conduction band energy level becomes denser, the electronic transition is more likely to occur, and the conductivity of the material is improved. The valence band of intrinsic 4H-SiC is mainly contributed by the 3p orbital of Si and the 2p orbital of C, the low energy interval of the conduction band is mainly contributed by the 3p orbital of Si, and the high energy interval is mainly powered by the electron transition in the 2p orbital of C. After the defect is introduced, a hybrid orbital is formed, and the peak value of the bandgap region in the density of states image appears to different degrees, which is equivalent to the introduction of different defect energy levels. The relative leftward translation of the Fermi level favors the higher energy conduction bands. According to Fourier's law, the conductivity of the three structures is calculated, and the conductivity of the 4H-SiC eigensystem is about 6.7 W/m/K, the conductivity of the 4H-SiC eigensystem is about 3.9 W/m/K, and the conductivity of the Si vacancy is about 2.09 W/m/K.