Misfit relaxation of InN quantum dots:: Effect of the GaN capping layer

The strain state on InN quantum dots (QDs) over GaN/sapphire substrates was analyzed by transmission electron microscopy. Changes in the in-plane lattice parameter of uncapped and capped InN QD heterostructures have been measured using moire fringe analysis. The uncapped QDs are almost completely relaxed, due to a misfit dislocation network present at the InN/GaN interface without generating any threading dislocations inside the QDs. In addition, a low-temperature-GaN capping process on InN QDs heterostructures was evaluated. Although this deposition avoids the InN decomposition, it modifies the QDs' morphology, decreases both the aspect ratio and, consequently, the plastic relaxation of the heterostructure.