Molecular Simulation Of Irradiation Effects On Different In_xGa_1-xN

In_xGa_1-xN has a higher absorption coefficient than other semiconductor materials.It is continuously adjustable and covers the band gap of the entire solar spectrum(0.7e V-3.4 e V),it is widely used in the production of multi-junction solar cells and the efficiency can reach 67%.In_xGa_1-xN material also has good resistance to radiation,but ion irradiation can still change the structure of In_xGa_1-xN material,optical properties,conversion efficiency and other properties.The fundamental reason of the impact of ion irradiation damage on the properties of In_xGa_1-xN lies in the change of the microstructure in In_xGa_1-xN,so the study of the microscopic damage mechanism of In_xGa_1-xN is very important.The author's research group and other experimental results show that the damage caused by ion irradiation in Ga N and In_xGa_1-xN will increase significantly with the increase of In composition.However,experimentally,the ion irradiation damage process that occurs in the order of picoseconds cannot be directly observed.The microscopic damage mechanism of In_xGa_1-xN is still unclear.In view of the lack of interatomic potential between In_xGa_1-xN atoms,there is no relevant In_xGa_1-xN ion radiation damage simulation reported.This work uses the molecular dynamics method(MD)combined with experimental research data,and uses the existing In_xGa_1-xN interatomic potential to compare In_xGa_1-xN at the microscopic level.The composition effect and radiation effect of have been simulated and explained,and the simulation results are in good agreement with the experimental results.The thesis work mainly includes two parts:1.In_xGa_1-xN component effect simulationThis part of the work has studied the reason why the anti-radiation performance of In_xGa_1-xN decreases with the increase of indium composition,and simulated and calculated In_xGa_1-xN(x = 0.3,0.5,0.7)threshold displacement energy,radiation damage process caused by a single recoil ion and overlapping cascades collision process.The simulation results show that:(1)As the composition of indium(x = 0.3 to x = 0.7)increases,the average threshold displacement energy of In_xGa_1-xN decreases slightly(41 e V To 34.6 e V);(2)The number of defects generated by a single recoil ion in In_xGa_1-xN increases as the composition of indium(x = 0.3 to x = 0.7)increases,but the increase is not large;(3)The dynamic annealing of indium-rich In_xGa_1-xN in the overlapping cascades collision is obviously suppressed.This result is consistent with the experiment.The analysis of defects in the overlapping cascades collision process shows that: the accumulation of defects in the indium-rich In_xGa_1-xN(x = 0.7)is faster and it is easier to form large clusters(these larger defect clusters are difficult to anneal during cascade collisions).In summary,we believe that the main reason why dynamic annealing is inhibited in In_xGa_1-xN of indium-rich materials is tthe increase in defect aggregation efficiency,which also leads to In_xGa_1-xN is an important reason why the anti-radiation performance decreases with the increase of the indium composition.2.Simulation of In_xGa_1-xN Irradiation EffectIn this part of the work,the effects of recoil ion energy and primary defects on the evolution process of In_xGa_1-xN radiation damage are studied.The effects of different recoil energies during radiation damage process,continuous radiation damage process under different overlapping recoil energy and initial defects of different sizes in In_xGa_1-xN are simulated.The evolution of clusters during irradiation.The results show that the greater the initial recoil energy,the greater the probability of multiple secondary cascade collisions during the recoil ion collision.When the recoil energy is greater than10 ke V,the simulated multi-cascade collision energy threshold is the same;Under the irradiation dose,the larger recoil energy will cause more radiation damage during the superimposed cascade collision process,and the defect aggregation efficiency will be improved;when the size of the defect cluster is certain,it will accumulate during the irradiation process,and during the annealing process,the small defect clusters will not grow or even disappear(the size of the defect clusters is related to the In composition).