A post-nucleation pause technique was described which reduced the density of coalesced islands (defects) in a quantum-dot ensemble without significantly altering the quantum-dot density. The growth conditions under which the quantum dots nucleated, were optimized so as to form high density quantum dots with a few defects. However, it was very difficult to prevent coalescence completely. Pausing the AsH3 flow for a few seconds after nucleation permitted surface adatoms to migrate from polycrystalline defect sites where the bond strengths were weak, to crystalline quantum-dot sites. This selective migration permitted the reduction of the defect density from 1.9 x 109/cm2 (0s pause) to an apparently defect-free quantum-dot ensemble (30s pause); while maintaining a quantum-dot density of more than 6 x 1010/cm2. A statistical analysis which was based upon atomic force microscopic images, high-resolution transmission electron microscopy and photoluminescence was used to characterize the effects of AsH3 upon the quantum-dot density and the crystallographic shape.

Selective Surface Migration for Defect-Free Quantum Dot Ensembles using Metal Organic Chemical Vapor Deposition. A.A.El-Emawy, S.Birudavolu, S.Huang, H.Xu, D.L.Huffaker: Journal of Crystal Growth, 2003, 255[3-4], 213-9