Simulations of dislocation density in silicon carbide crystals grown by the PVT-method

The Alexander-Haasen (AH) model has been applied to analyze the plastic deformation and dislocation generation during the crystal growth process of 4H-SiC (silicon carbide). Plastic parameters are obtained by fitting the predicted curves to the experimental data on the plastic deformation of alpha-SiC crystals under uniaxial compression. The relationship between the activity energy (Q) and stress exponent (n) is considered when using the AH model. This relationship explicitly represents two deformation mechanisms around the critical temperature. The ratio of the activity energy and stress exponent, Q/n, equals 0.3 eV when the temperature is below the transition temperature, and 1.3 eV when the temperature is above the transition temperature. Then, the model is used to predict the dislocation density and thermal stresses in the crystals. The largest dislocation density is found to occur near the graphite/SiC interface, and the dislocation density gradually decreases with the thickness of the ingot.