Deformation of 4H-SiC: The role of dopants

The role of dopants on deformation and mechanical properties of 4H silicon carbide (4H-SiC) is proposed by using nanoindentation. It is found that the hardness, elastic modulus, and fracture toughness of 4H-SiC substrate wafers all decrease on the order of vanadium (V) doping, undoping, and nitrogen (N) doping. For all three types of 4H-SiC, basal plane dislocations (BPDs), threading edge dislocations, and cracks are formed during the nanoindentation. Polymorph transitions from 4H-SiC to amorphous SiC and 3C-SiC are found as the penetration depth of the indent increases from the subsurface to the deeper region. N doping is found to weaken the bond strength of 4H-SiC, which enhances the glide and piling up of BPDs in nanoindentated N-doped 4H-SiC. In contrast, V doping effectively hinders the glide of BPDs, which accumulates a high-stress field and facilitates the polymorph transition from 4H-SiC to 3C-SiC and amorphous SiC. The insight on the effects of dopants on the deformation and mechanical properties of 4H-SiC may help the design of the processing of differently doped 4H-SiC substrate wafers.