Comparison of the spiral growth modes of silicon-face and carbon-face silicon carbide crystals

• In silicon carbide we found that the dependence of the terrace width of growth spirals on supersaturation is different for silicon and carbon faces.
• Si-face growth spirals follow the model of Burton, Cabrera and Frank.
• The maximum terrace width of C-face growth spirals is independent of supersaturation.
• The terrace width of C-face crystals depends on the radius and we provide a model which may explain that feature.

We have studied the dependence of the terrace width of growth spirals on local supersaturation during the growth of on-axis silicon carbide (SiC) crystals. Local supersaturation is adjusted by changing the residual argon gas pressure inside the sublimation growth chamber. Whereas Si-face crystals seem to partly verify the model of Burton, Cabrera and Frank, we found that on C-face crystals, the terrace width is independent of supersaturation. In contrast to previously reported data obtained from KDP crystals, we cannot ascribe our result to hollow-core dislocations or micropipes, as the observed growth spirals arose from independent and closed, unit or double-unit screw dislocations. Besides, we checked that neither the finite growth area nor the influence of the stress field of the dislocation can explain our data.