Nucleation sites of recombination-enhanced stacking fault formation in silicon carbide p-i-n diodes

The morphology and nucleation sites of stacking faults formed during the forward operation of 4H silicon carbide p-i-n diodes were investigated using optical emission microscopy (OEM) and transmission electron microscopy (TEM). Partial dislocations bounding the stacking faults are mostly aligned to the <11-20> directions with Burgers vectors of the 1/3<1-100> type. Arrays of dislocation half loops in the blocking layer serve as nucleation sites of double-rhombic stacking faults. The morphology of these stacking faults indicates that short basal plane segments associated with threading dislocations are the origin of rhombic stacking faults. All dislocations in a half-loop array have the same Burgers vector and nucleate on a single basal plane, which was evidenced by the merging of double-rhombic stacking faults. Most pre-existing basal plane dislocations within the blocking layer which are visible in OEM images dissociate to form stacking faults during the degradation. Basal plane dislocations aligned along the off-cut direction form rectangular stacking faults, while others break up into partial dislocation segments along the <11-20> directions, which are often wedge-shaped. Thus, all nucleation sites of the stacking faults correspond to pre-existing dislocation segments residing in basal planes. The morphology and evolution of double-rhombic stacking faults indicate that the p-i-n diode degradation cannot be driven by stress in the structure. (C) 2004 American Institute of Physics.