Formation of basal plane stacking faults on the (0001¯) facet of heavily nitrogen-doped 4H-SiC single crystals during physical vapor transport growth

The formation of stacking faults in heavily nitrogen-doped (mid-1019 cm−3) 4H-SiC boules grown by the physical vapor transport (PVT) growth method was investigated by studying surface morphologies on the (0001¯) facet of the boules. Low-voltage scanning electron microscopy (LVSEM) observations detected stacking faults on the (0001¯) facet of heavily nitrogen-doped 4H-SiC crystals. LVSEM and atomic force microscopy (AFM) studies revealed that the stacking faults showed characteristic morphologies, which stemmed from the interaction between stacking faults and surface steps. These observations also revealed that heavy nitrogen doping resulted in the nucleation of a number of surface hillocks on the (0001¯) facet; the hillocks were never observed on the facet of conventionally doped (nitrogen concentration: mid-1018 cm−3) 4H-SiC boules. Furthermore, the hillocks were nucleated only on the facet and never observed on the outer regions of the facet. Based on these results, the stacking fault formation mechanism in heavily nitrogen-doped 4H-SiC crystals is discussed.