Abstract
Results of calculations on thermal stresses induced during pulling of GaAs ingots are reported. Comparison between these calculations and our experimental results shows that the dislocations nucleation in crystals during growth cannot be directly related to a constant value of the critical resolved shear stress (CRSS). According to experiments performed on other materials, it is concluded that the CRSS can strongly depend upon the initial state of the material, and particularly upon temperature and native defects concentration and mobility.