Molecular Dynamics Simulation Of Irradiation-induced Microdefects In Ⅲ-Ⅴ Semiconductor Materials

The core components of space-use systems,represented by charge coupled devices（CCDs）,solar cells（SCs）and light-emitting diodes（LEDs）,are subject to irradiation damage during orbital operation,leading to degradation or even failure of the devices.One of the main reasons for the performance of optoelectronic devices is the displacement damage effect of materials in the space environment,where irreversible defects generated and accumulated through irradiation can lead to degradation of the relevant electrical,optical and even mechanical properties of the device.In other words,the study of the evolution of the defect generation and accumulation in the material structure under various factors and the influence mechanism is undoubtedly a key part of the exploration of the mechanism of the irradiation damage effect.In this paper,the generation,evolution and accumulation of displacement damage defects and the influencing mechanism of displacement damage defects are analysed in depth through molecular dynamics simulations of single particle initial displacement damage and heavy ion irradiation simulations of semiconductor materials under different material and factor conditions,with the following results.GaAs,3C-Si C and Ga N were used as research objects to carry out simulation studies of displacement thresholds and defect formation under different crystal orientations.The simulation results show that there are peaks in E_d values between each high symmetry direction,with Si and N PKA having significant anisotropy and large variations,and the formation of defects mainly in the form of Frenkel pairs of defect types.In addition,the differences in E_d values between the semiconductors lead to the most severe amorphisation in the damaged region of GaAs,followed by 3C-Si C and the lowest in Ga N during the single-particle initial displacement damage.The simulations of single-particle initial displacement damage under different irradiation temperatures and nitrogen doping concentrations were carried out using GaAs as the research object.The simulation results show that,unlike the behaviour of high E_PKA damage,high temperatures increase the Frenkel pair peak（N_p）and continuously reduce the number of steady-state defects（N_s）,implying that high temperatures promote the compounding behaviour of defects.In terms of defect distribution,the behaviour of large vacant clusters breaking down into smaller clusters and point defects occurs at high temperatures,while interstitial defects show interconversion between clusters.In addition,the persistent nitrogen doping behaviour also reduces the N_s of GaAs_1-xN_x,increases the E_d value to some extent and reduces the extent of damage,showing the aggregation behaviour of large clusters in the defect distribution.Heavy ion irradiation simulations as well as tensile simulations of irradiated structures were carried out with GaAs NWs as the object of study.The simulation results show that the irradiated defects of GaAs NWs show an overall"hollow centre,dense surrounding"defect distribution,but with the increase of single ion energy,the number of steady-state defects tends to increase and then decrease,and this phenomenon gradually disappears as the size of GaAs NWs continues to increase.In addition,defects accumulate rapidly at low ion doses and start to show saturation with increasing injection,while GaAs NWs undergo erosion refinement and amorphization is the main mode of structural transformation,which is more evident at high energy ion damage.The irradiation effect has a direct impact on the mechanical properties of GaAs NWs,with increasing heavy ion dose,GaAs NWs yield strength and Young’s modulus show a trend of first decreasing and then stabilizing.