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

Abstract

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.