We discuss a post-nucleation pause technique that reduces the density of coalesced islands (defects) in a quantum dot (QD) ensemble without significantly altering the QD density. The growth conditions under which the QDs nucleate, are optimized to form high density QDs with few defects, however, it is very difficult to prevent coalescence completely. Pausing the AsH3 flow for a few seconds after nucleation allows surface adatoms to migrate from polycrystalline defect sites where the bond strengths are weak to crystalline QD sites. This selective migration allows the reduction of defect density from 1.9 X 10(9)/cm(2) (0 s pause) to apparently defect-free QD ensemble (30 s pause) while maintaining a QD density > 6 x 10(10)/cm(2). We will discuss statistical analysis based on atomic force microscope images, high-resolution transmission electron microscopy and photoluminescence to characterize the effects of AsH3 pauses on the QD density and crystallographic shape. (C) 2003 Published by Elsevier Science B.V.