Millisecond Laser-induced Damage To Gallium Arsenide Materials

Nowadays,GaAs material is used more and more in the aerospace and military fields.As one of the raw materials for solar cells,the solar cell made by GaAs has the best conversion efficiency.And laser induced damage has been a hot issue in scientific research for many years.At present,there is a few research about the millisecond laser induced damage on GaAs material.In order to figure out the mechanism of the millisecond induced damage on GaAs,we investigate the effects of thermal and thermal stress caused by the incident laser via experiment and numerical simulation.The numerical model of temperature filed in the GaAs wafer during the laser irradiation is constructed based on the three dimensional heat conduction equation.The results show that the threshold of GaAs for the 1064nm,1ms laser is 61.5J/cm2.Through the model,the information of the phase transition process such as melting,re-solidification,and the melting radius and melting depth of the material at different energy densities were obtained.Besides that,the experiment is set up to measure the temperature of the spot center of the laser with the infrared thermometer.The experimental results show that temperature rise curve is consistent with the results of the model,which verifies the accuracy of the model.Taking the crystal structure of the GaAs into account,the thermal stress field model is constructed based on the temperature field model.The 12 slip systems can be obtained to describe the dynamic change process of resolved shear stress field of GaAs during the laser irradiation.The results show that the thermal slips are firstly activated below the spot area of laser when the thermal shear stresses of slip systems surpass the critical yield stress,and this comes out before the melting of GaAs surface.Brittle cracks occur in the initiation points offered by the thermal slips.The calculated stresses distribution indicate that the fracture mostly occurs at the boundary of the laser spot and the center,which is consistent with the experimental result.The results of this paper are meaningful to further research of the millisecond laser induced damage on GaAs.