Dislocation analysis of germanium wafers under 1080  nm laser ablation

COMSOL Multiphysics was employed to establish a dislocation model based on the Alexander and Haasen (AH) model, the heat conduction equation, and Hooke's law for calculating the dislocation distribution of germanium (Ge) under laser irradiation. The numerical simulation results were obtained. A continuous 1080 nm laser was utilized to ablate the monocrystalline Ge wafers to validate the model. The experimental results show that no surface damage appears until the irradiances go up to 234W/cm² for 100 ms laser ablation. This is consistent with the numerical findings. The initiation times of surface damage by the experiments at 234W/cm² and above agree well with the numerical results, which means that the model can efficiently predict the dislocation field.