Structure and distribution of secondary defects in high energy ion implanted 4H-SiC

The structure, size, and distribution of the secondary defects in high-energy B⁺ or Al⁺ implanted 4H-SiC were investigated by cross-sectional transmission electron microscope observations and secondary ion mass spectrometry analyses. Three types of defect structure were detected. The first (type I) is an extrinsic Frank partial dislocation loop parallel to {0001} and is same as that observed in kilo-electron-volt energy B⁺ or Al⁺ implanted SiC. The second (type II) is also an extrinsic dislocation loop with an extra Si-C bilayer parallel to {0001} but it has not been previously reported. The last type (type III) has no extra Si-C bilayer. The type of defect is correlated to the size of it. When the size is larger than about 12 nm, the defect becomes type I or type II and the defects which are smaller than about 12 nm are type III. The range of the secondary defect size depends on implanted ions and its dose. The maximum size of defects grows with dopant concentration and that in B+ implanted sample is larger than that in Al⁺ implanted one at the same volume concentration of dopant. But the minimum size of defects seems independent of dopant concentration and ion species. It is 2-4 nm in any case. These defects are distributed in the deeper region of projected range for low dose implantation. On the contrary, they are distributed from near surface for high dose implanted samples.