Observation of V Defects in Multiple InGaN/GaN Quantum Well Layers

Multiple In0.18Ga0.82N (4 nm)/GaN (40 nm) quantum well (QW) layers in a green laser diode were observed by high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) and conventional transmission electron microscopy. HAADF-STEM provided undoubted evidence that V defects in the multiple QW have the thin six-walled structure with InGaN/GaN {10\11} layers. The detailed structure of the observed V defects is discussed on the basis of the formation mechanism of V defects which was proposed taking into account the growth kinetics of the GaN crystal and a masking effect of In atoms segregated around the threading dislocation (Shiojiri et al. J. Appl. Phys. 99, (2006) 073505).