Deformation of 4H-SiC: The role of dopants
Xiaoshuang Liu, Junran Zhang, Binjie Xu, Yunhao Lu, Yiqiang Zhang, Rong Wang, Deren Yang, Xiaodong Pi
Abstract
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.