Nucleation Mechanism and Evolution of Spindle Defect During Homoepitaxy of 4H-SiC on Carbon-Face Substrates

The nucleation and evolution mechanisms of a newly identified morphological defect, termed the spindle defect, are elucidated during the homoepitaxy of 4H-SiC on carbon(C)-face substrates. The spindle defect is predominantly composed of 3C-SiC and is nucleated by the disturbances of step-flow growth induced by downfall events. The lattice and thermal expansion mismatches between the 3C-SiC spindle defect and the 4H-SiC epilayer give rise to severe compressive stress and local doping variations in the adjacent 4H-SiC matrix. Driven by this intense local stress, high density of Shockley-type stacking faults (SSFs) and dislocations nucleate around the spindle defect. During subsequent epitaxy, dislocation slip coupled with step-flow motion drive the continuous expansion of these SSFs, forming distinctive concentric-elliptical shaped SSFs and dislocation networks. Consequently, the spindle defect not only causes the immediate failure of the power device containing the defect, but also introduces the long-term bipolar reliability issues of adjacent devices due to spindle-defect-concomitant SSFs. By elucidating the nucleation and evolution mechanisms of the new spindle defect, this work provides insights into high quality C-face epitaxy of 4H-SiC.