Observation of V defects in multiple InGaN/GaN quantum well layers

Multiple In(0.18)Ga(0.8)2N (4 nm)/GaN (40 nm) quantum well (QW) layers in a green laser diode were observed by high-angle annular darkfield (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 (1) over bar1} 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).