A post-nucleation pause technique was discussed that 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 nucleate, were optimized to form high density quantum dots with few defects, however, it was 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 were weak to crystalline quantum-dot sites. This selective migration allows the reduction of defect density from 1.9 x 109/cm2 (0s pause) to apparently defect-free quantum-dot ensemble (30s pause) while maintaining a quantum-dot density >6 x 1010/cm2. A statistical analysis based upon atomic force microscopic images, high-resolution transmission electron microscopy and photoluminescence was used to characterize the effects of AsH3 on the quantum-dot density and 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