Structural analysis of interfacial dislocations and expanded single Shockley-type stacking faults in forward-current degradation of 4H-SiC p-i-n diodes

The structure of interfacial dislocations (IDs) formed at different depth and expansion of single Shockley-type stacking faults (1SSF) from the IDs in forward-current degradation of 4H-SiC p-i-n diodes were investigated. IDs showing different contrast in X-ray topography (XRT) were formed during p-i-n diode fabrication processes. From a high-resolution observation using a transmission electron microscopy, it was clarified that IDs observed by different contrast in XRT were different in the formation interface although they had the same Burgers vector of 1 3 [ 11 2 ¯ 0 ] and Si-core type. The ID with brighter contrast in XRT were formed at the shallower interface between p+ anode and n− drift layers, whereas darker contrast ones were formed at the deeper interface between n− drift and n+ buffer layers. Expansion of the 1SSFs originated from the IDs which were formed at the shallower interface occurred under the condition of lower stress-current density than 25 A cm−2, whereas that originated from ID which were formed at the deeper interface was caused under the condition of higher stress-current density than 1200 A cm−2. These results indicated that IDs were formed at different depths during device processes, and 1SSF expanded from these IDs under various stress-current conditions.