Suppression of Polytype Transformation with Extremely Low-Dislocation-Density 4H-SiC Crystal in Two-Step Solution Method

摘要

We achieved the growth of extremely-high quality SiC crystal with two-step solution method with specially-designed seed crystals. The two-step growth consists of 1~(st) step growth on Si-face for the reduction of threading dislocations and 2~(nd) step growth on C-face for the reduction of basal plane dislocations and thickening. In this method, we can make the dislocation density extremely low, while the polytype easily changes during growth due to the absence of spiral hillocks originating from threading screw dislocation (TSD). In this study, we prepared specially designed seed crystals for both 1~(st) and 2~(nd) growth steps to provide steps continuously. In the seeds, a few TSDs exist at the upper-side of the step structure. Consequently, we demonstrated the suppression of the polytype transformation during the C-face growth with extremely low-dislocation-density crystal. Accordingly, we successfully obtained extremely low-dislocation density 4H-SíC with TSD, TED and BPD density of 11, 385 and 28 cm~(-2).