Glide and multiplication of basal plane dislocations during 4H-SiC homoepitaxy

Basal plane dislocations (BPDs) are an important category of extended defects in SiC epilayers. They act as nucleation sites for single layer Shockley-type stacking faults which account for the degradation of the bipolar devices operating under forward bias. It is well documented that most of the BPDs in the SiC epilayers propagate from the substrates. However, two characteristic types of BPDs were suggested to be due to either nucleation or multiplication during epitaxy, including interfacial dislocations and short BPD arrays connected to the epilayer surface by threading segments. Combining molten KOH etching, plan-view transmission x-ray topography, and photoluminescence mapping, both types are determined to be two parts of one defect produced by the sideway glide of a BPD under the influence of shear stress. During the glide, the down-step end of the BPD frequently produces a series of short BPD segments at the moving growth front. These BPD segments will grow into an array of dislocation half loops. At the same time, the sideway glide of the BPD in the epilayer leaves an edge-type BPD segment at the epilayer∕substrate interface, which is the interfacial dislocation. The defect morphology provides the evidence of significant level of shear stresses present in SiC homoepitaxy of typical power device structures. The magnitude of such stresses is estimated.