Enhanced photoluminescence of InAs self-assembled quantum dots grown by molecular-beam epitaxy using a 'nucleation-augmented' method

A two-stage “nucleation-augmented” growth method for producing InAs self-assembled quantum dots (QDs) using molecular-beam epitaxy on GaAs (100) substrates has been investigated in detail. Photoluminescence (PL) measurements show that a 1.8-monolayer-(MLs) InAs QD “nucleation” layer grown at a fast rate, followed by a 2.6-MLs-InAs “augmented” layer grown under pulsed conditions at a slow rate, dramatically increases the dot density and improves the PL intensity for the InAs QDs. It was found that, when the effective growth rate of the InAs augmented layer was reduced, the PL peak emission shifts to a longer wavelength and the PL intensity is enhanced. These changes in characteristics were attributed to improved optical quality and greater dot density.