Formation mechanism of V defects in the InGaN/GaN multiple quantum wells grown on GaN layers with low threading dislocation density

V-defect formation of the InxGa1-xN/GaN multiple quantum wells (MQWs) grown on GaN layers with different threading dislocation (TD) densities was inve stigated. From cross-sectional transmission electron microscopy, we found t hat all V defects are not always connected with TDs at their bottom. By inc reasing the indium composition in the InxGa1-xN well layer or decreasing th e TD density of the thick GaN layer, many V defects are generated from the stacking mismatch boundaries induced by stacking faults which are formed wi thin the MQW due to the strain relaxation. Also, TD density in the thick Ga N layer affects not only the origin of V-defect formation but also the crit ical indium composition of the InxGa1-xN well on the formation of V defects . (C) 2001 American Institute of Physics.