Comparing basal and prismatic slips induced by thermal stresses in 4H-SiC crystals

Basal and prismatic slips induced by thermoelastic stresses during the growth of 4H-SiC are investigated by using the finite element method (FEM) and considering factors such as the crystal diameter, temperature, and off-axis angle. It is found that with the increase of the crystal diameter from 6 to 8 inches, the prismatic slip more likely occurs, leading to a higher density of basal plane dislocations (BPDs). However, the basal slip hardly changes. The temperature difference, rather than the growth temperature, is the primary factor contributing to the increase in the slip stresses. The stresses of the basal slip are significantly affected by a small off-axis angle, whereas those of the prismatic slip are not unaffected until the off-axis angle reaches 30 degrees. The mechanism for the decrease of the density of BPDs along the growth direction in an 8 inch 4H-SiC crystal is elucidated. We verify that the prismatic slip in an 8 inch 4H-SiC crystal contributes more to the BPD formation than the basal slip.