A study was made of how threading dislocations in an underlying GaN epilayer affected the surface morphology of InGaN/InGaN quantum-well structures which were grown by means of low-pressure metal-organic vapour phase epitaxy. When the GaN growth pressure was increased from 100 to 400Torr, the density of pure edge and mixed threading dislocations was reduced. However, the density of pure screw threading dislocations simultaneously increased. The quantum-well surface morphology depended strongly upon the densities of mixed or screw threading dislocations in the underlying GaN epilayer. It was found that the pit density on the surface of quantum-well structures decreased with a decreasing density of mixed threading dislocations, and that the quantum-well surface morphology then exhibited a pattern of large nanoscale islands if the density of screw threading dislocations simultaneously increased, or a pattern of heavily bunched steps if it was unchanged.

Morphological Evolution of the InGaN-Based Quantum Well Surface due to a Reduced Density of Threading Dislocations in the Underlying GaN through Higher Growth Pressure K.Uchida, J.Gotoh, S.Goto, T.Yang, A.Niwa, J.Kasai, T.Mishima: Japanese Journal of Applied Physics - 1, 2000, 39[4A], 1635-41