Molecular Dynamics Study On Defect Evolution Of P-type Doping And High-energy Irradiation Of Silicon Carbide

As a third-generation wide band gap semiconductor material,silicon carbide(Si C)has broad application prospects in the manufacturing of high-frequency transistors and optoelectronic devices.However,the development of Si C related devices is generally restricted by high concentrations of various defects in this material.Ion implantation,nowadays as the only technique that be used as selective doping,is one of the main reasons causing defects in Si C-based power devices.For p-type implantation,the high compensation rate of defect formed after annealing is still a world-wide problem to be solved due to the influence of doping dose and other factors,and the research on the damage formation and evolution mechanism behind it under atomic-level simulation is still in the blank.On the other hand,as a main inert matrix for the transmutation of plutonium and other radioactive wastes,it is an important premise for the application of Si C in some extreme conditions to study its damage evolution and electron-phonon coupling effect under high-energy ion irradiation,and evaluate the tolerance of the material under extreme irradiation environment.This thesis focuses on the above problems to carry out relevant molecular dynamics research to deeply understand the formation and evolution of damage under p-type doping and annealing of Si C and the damage evolution under high-energy irradiation.The specific contents include:(1)The ionization energy loss was introduced into classical molecular dynamics to explore the phenomenon of atomic displacement cascade in the process of p-type ion implantation in order to improve the simulation accuracy.The physical formation mechanism of ion implantation damage and self-repair were explained from the perspectives of thermal spike effect,phonon propagation and local stress evolution,the artifact phenomenon of identifying interstitials and vacancies by classical WS method was clarified.(2)An effective measurement method of defect damage in high temperature annealing simulation was proposed.The recrystallization process during high temperature annealing under different doses was explored,and the reasons for the deterioration of lattice quality,area separation and dislocation slip during post annealing were successfully explained;(3)Effective methods to further improve the lattice quality were explored.At the same time,aiming at the thorny problem of high defect compensation rate in p-doped silicon carbide,the types of lattice defects surrounding dopants and the statistics laws of doping efficiency were carried out,and the factors limiting carrier life in practical processing were also clarified;(4)The theoretical model of high energy implantation was established.Based on the ionization energy loss,two-temperature model was introduced to explore the damage cascade evolution irradiated by single ion with different energy and the feedback of electronic subsystem,and the specific influence of different electronic stopping ability on the formation of internal damage in the system is obtained.The feedbacks of atomic and electronic subsystems in different stages under continuous and overlapping irradiation were explored,which provided reasonable explanations for the distribution of ion irradiation damage in experimental studies.The correlations between the atomic orientation,lattice arrangement density,damage formation,stress evolution and subsystem temperature were all systematically explored.