Real-time in situ observation of extended defect evolution near a crack tip in GaSb crystal under thermal loading

When an AlAsSb/InAs superlattice semiconductor material is grown by molecular beam epitaxy, extended defects in the GaSb buffer layer are inevitable. Therefore, the study the formation and evolution of extended defects is considerably important. In this study, a crack tip located in the buffer layer was considered. The evolution process of nucleation as well as development and extinction of two extended defects on the (1 1 −1) and (−1 1 −1) faces were observed in real time in situ by scanning transmission electron microscopy during heating. Analysis of the stress field results showed that thermal stress is the driving force for the propagation of extended defects, which promotes the nucleation and evolution of the (1 1 −1) and (−1 1 −1) surface extended defects. The variation in crack width before and after heating was measured according to the intensity of the atomic and crack regions in the high-resolution STEM-BF image. The results showed that the crack closes after heating at a high temperature compared to room temperature. It is considered that the amorphous GaSb at the crack tip and the edge portion at the nanometer scale during the heating process is transformed into a single crystal, thus causing the crack to shrink.