Abstract：According to the existing irradiation simulation and theoretical analysis results, molecular dynamics method is used to establish an effective irradiation approach to simulate the damage of wurtzite GaN materials in long-term low-dose neutron irradiation. First, the cascade collision process of GaN material subjected to different initial irradiation energies is simulated. The relationship between point defects and initial energy of PKA, and the evolution process of point defects are analyzed. By setting a number of recoil atoms with certain spatial distribution, whose energy is equivalent to the irradiation energy, a more realistically uniform distribution of irradiation damage is realized. The cascade process is then iterated to obtain the damage accumulation models of GaN materials under long-term low-dose irradiation. Using this computational approach, nano-indentation simulations of GaN materials under different irradiation doses are carried out, and the variations in the mechanical properties and the deformation mechanisms are investigated. Our study indicates that adopting five recoil-atoms with a proper spatial distribution can improve the computational efficiency and obtain an uniform irradiation damage distribution. It is obvious that the changes in mechanical properties are directly related to the defects caused by irradiation. The elastic modulus and indentation hardness of the c-plane of GaN before and after irradiation are higher than that of the m-plane. Under a relatively low irradiation dose, the elastic moduli of the c-plane and m-plane of GaN material increase slightly due to the hindering of dislocation nucleation and motion by the irradiation defects. However, with the increase of irradiation dose, the size of the amorphized regions increases which leads to the decreasing in the elastic modulus of GaN materials. A large number of disordered amorphous structures and the defect clusters are generated inside the GaN materials, which induces a decrease in indentation hardness of GaN after irradiation.
2023, Vol. 44 
